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Question 1
ప్రశ్న 1
Which Indian Standard is the principal specification currently applicable to chemical and air-entraining admixtures for concrete, including superplasticizers?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 9103:1999 is the applicable Indian Standard specification for concrete admixtures and remains listed by BIS as the current standard. Its scope covers chemical and air-entraining admixtures, including superplasticizers, supplied in forms such as solids, liquids or emulsions. IS 10262 deals primarily with concrete mix proportioning rather than specification of admixture performance. IS 383 specifies aggregates, while IS 516 deals with concrete testing. Therefore Option A is the correct code reference for this question.
వివరణ:
Question 2
ప్రశ్న 2
Which description most accurately represents an admixture in the context of IS 9103?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
An admixture is introduced into a concrete or mortar batch immediately before or during mixing to modify one or more properties in the plastic or hardened state. The definition distinguishes admixtures from the basic constituents such as water, aggregates and hydraulic cement. It also distinguishes the chemical-admixture concept from materials such as pozzolanic or slag additions and fibre reinforcement identified separately in the standard definition. Admixtures may modify workability, setting, strength development, air content or other performance characteristics. Hence Option B best represents the technical meaning.
వివరణ:
Question 3
ప్రశ్న 3
Which effect most directly characterizes an accelerating admixture?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
An accelerating admixture is intended to increase the rate of hydration, shorten setting time, or increase the rate of hardening or strength development. These effects can be useful when early finishing, early formwork removal or rapid strength gain is important. Acceleration does not mean that the admixture must also be a high-range water reducer. Air entrainment is a different function involving the intentional creation of small air bubbles. Therefore Option C correctly identifies the defining performance of an accelerator.
వివరణ:
Question 4
ప్రశ్న 4
Concrete must attain useful early strength rapidly during cold-weather construction, while proper temperature protection and curing will also be provided. Which admixture type is most directly suited to this objective?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
An accelerating admixture can increase the rate of early hydration and strength development and is therefore relevant when early strength is required in cold conditions. It may also shorten setting time, depending on the product and dosage. An accelerator does not replace the need to protect fresh concrete against freezing or to provide proper curing temperature. A retarder would generally act in the opposite direction by delaying setting. Consequently Option B is the most appropriate selection for the stated objective.
వివరణ:
Question 5
ప్రశ్న 5
During hot-weather concreting, a long haul and placement period creates a risk of concrete setting before proper placing and finishing are completed. Which admixture function is most appropriate?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A retarding admixture delays the setting of cement paste and therefore of the concrete containing it. This can be useful in hot weather, long transportation periods or placements where additional working time is required. The retarder must nevertheless be selected and dosed through trials because temperature, cement chemistry and dosage can strongly influence its effect. Excessive retardation can create construction difficulties if the setting delay becomes too long. Option A therefore matches the field requirement described.
వివరణ:
Question 6
ప్రశ్న 6
Which statement correctly defines the principal action of a water-reducing admixture or workability aid?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A water-reducing admixture can be used either to obtain greater workability at a given water content or to maintain required workability while reducing water content. The second mode can permit a lower water-cement ratio if cement content is held appropriately, which may improve strength and durability. Water reduction should not be confused with deliberate air entrainment, although some products can have secondary effects that must be checked. Setting-time behavior can also vary with admixture chemistry and dosage, but it is not the defining feature of a water reducer. Therefore Option A correctly states the fundamental function.
వివరణ:
Question 7
ప్రశ్న 7
Under the IS 9103 water-reduced concrete performance requirement, a water-reducing admixture may use at most 95 percent of the control-mix water content. If the control concrete contains 200 kg/m³ of water, what is the maximum corresponding water content of the test mix?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The specified maximum is 95 percent of the water content of the control concrete. Therefore the maximum permitted test-mix water is 0.95 × 200 = 190 kg/m³. This corresponds to a minimum water reduction of 5 percent relative to the control under this performance comparison. The calculation concerns the IS 9103 test requirement and should not be interpreted as the optimum field dosage for every concrete. Hence Option C is correct.
వివరణ:
Question 8
ప్రశ్న 8
For a superplasticizing admixture evaluated in a water-reduced concrete mix under IS 9103, the water content may be at most 80 percent of the control value. If the control mix requires 180 kg/m³ of water, what is the corresponding maximum water content?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For the stated performance comparison, the test-mix water content is limited to 80 percent of the control value. Multiplying 180 by 0.80 gives 144 kg/m³. The reduction relative to the control is therefore 36 kg/m³, which represents 20 percent of 180 kg/m³. This illustrates why superplasticizers are commonly described as high-range water-reducing admixtures. Option C is the correct calculated value.
వివరణ:
Question 9
ప్రశ్న 9
A structural concrete mix already satisfies its maximum water-cement ratio but requires much higher workability for placement through congested reinforcement. Which approach best uses a superplasticizer?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A superplasticizer can impart very high workability without requiring a corresponding increase in water content. This is particularly useful where a concrete already has a restricted water-cement ratio for strength or durability. Simply adding water would raise the water-cement ratio and may impair strength, permeability and durability. Superplasticizer dosage and compatibility still need to be established by trial because excessive dosage can cause undesirable behavior. Thus Option B represents the correct engineering application.
వివరణ:
Question 10
ప్రశ్న 10
What principally distinguishes a retarding superplasticizing admixture from a normal superplasticizing admixture in IS 9103 terminology?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A retarding superplasticizing admixture combines high-range water-reducing or high-workability action with prolonged workability retention and retarding behavior. This can be useful where concrete must remain workable for longer periods before placement and compaction. A normal superplasticizer is not defined by the same deliberately retarding performance. Neither type is intended to require an increased water-cement ratio. Therefore Option A correctly identifies the important distinction.
వివరణ:
Question 11
ప్రశ్న 11
What is the principal mechanism and common durability benefit of an air-entraining admixture?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
An air-entraining admixture intentionally creates a system of numerous small air bubbles during mixing. Properly distributed entrained air can provide space that relieves hydraulic pressures associated with freezing water in saturated concrete. This can substantially improve freeze-thaw resistance when the concrete is otherwise properly designed and cured. Air entrainment can also improve cohesion and workability in many mixes. Option A therefore correctly combines the mechanism and its important durability application.
వివరణ:
Question 12
ప్రశ్న 12
If all other important mix variables are held essentially constant, what is the usual effect of substantially increasing the entrained-air content beyond that actually required?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Entrained air introduces additional void volume into the hardened cementitious system. If other important variables are held essentially constant, excessive air generally reduces compressive strength because the solid load-carrying fraction is reduced. The beneficial amount of air therefore has to be controlled rather than maximized without limit. In freeze-thaw applications the durability advantage must be balanced against strength and other performance requirements. Option A correctly describes the usual engineering consequence of excessive entrained air.
వివరణ:
Question 13
ప్రశ్న 13
Which statement concerning chloride in concrete admixtures is most consistent with IS 9103 principles?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 9103 requires the chloride content of an admixture to be declared by the manufacturer. The standard specifically warns that admixtures containing relatively large amounts of chloride may accelerate corrosion of prestressing steel. It also indicates that superplasticizers are expected to be chloride free. For reinforced concrete, total chloride in the concrete must remain within the applicable IS 456 limits. Therefore Option B reflects the important durability and corrosion issue correctly.
వివరణ:
Question 14
ప్రశ్న 14
Before adopting an admixture for a particular concrete, which group of properties does IS 456 specifically require to be established in trial mixes with and without the admixture?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 456 requires the workability, compressive strength and slump loss of concrete with and without the admixture to be established during trial mixes. This recognizes that an admixture can interact differently with different cements, supplementary materials, temperatures and mix proportions. A product that performs well in one concrete cannot automatically be assumed to behave identically in another. Trial mixtures therefore provide evidence of both the desired benefit and any undesirable side effect. Option A correctly lists the properties explicitly emphasized by the code.
వివరణ:
Question 15
ప్రశ్న 15
An admixture dosage is specified as 0.8 percent by mass of cement. If the concrete contains 420 kg/m³ of cement, what admixture mass is required per cubic metre?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A dosage of 0.8 percent corresponds to a mass fraction of 0.008. Multiplying 420 kg/m³ of cement by 0.008 gives 3.36 kg/m³ of admixture. The calculation is based on the stated dosage being expressed relative to cement mass. Actual field dosage must still remain within the product recommendation and must be confirmed for the required concrete performance. Therefore Option C is the correct numerical answer.
వివరణ:
Question 16
ప్రశ్న 16
A concrete requires 180 kg/m³ of effective mixing water. A liquid admixture dosage is 5 kg/m³, and 60 percent of that admixture mass is water that is to be counted as part of the batch water. Ignoring other moisture sources, how much separate mixing water should be added?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The liquid admixture contributes 5 × 0.60 = 3 kg/m³ of water. That water must be included when the total effective batch-water requirement is being controlled. The separately added mixing water is therefore 180 − 3 = 177 kg/m³. Adding the full 180 kg/m³ separately would give 183 kg/m³ of total water under the assumptions stated. Hence Option B is correct.
వివరణ:
Question 17
ప్రశ్న 17
Which quality-control requirement for liquid admixtures is correctly associated with IS 456?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 456 specifies that the relative density of liquid admixtures should be checked for each drum and compared with the specified value before acceptance. It also requires the chloride content of admixtures to be independently tested for each batch before acceptance. These checks help control uniformity and reduce the risk of accepting a product that differs materially from the approved supply. They are especially relevant because dosage is often small relative to the total concrete mass, so variations can still have significant effects. Therefore Option A states the appropriate quality-control requirements.
వివరణ:
Question 18
ప్రశ్న 18
Two different chemical admixtures are proposed for simultaneous use in the same concrete. What is the technically appropriate procedure?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Two admixtures that perform satisfactorily on their own may interact when used together. IS 456 therefore requires data to be obtained to assess their interaction and ensure compatibility when two or more admixtures are used simultaneously. Relevant trials may examine workability, slump retention, setting, air content and strength as appropriate to the application. Addition sequence can also influence performance and should follow validated recommendations rather than arbitrary mixing. Option B is consequently the technically sound procedure.
వివరణ:
Question 19
ప్రశ్న 19
Match the admixture type with its principal function:
1. Accelerator
2. Retarder
3. Water reducer
4. Air-entraining admixture
P. Delays setting
Q. Intentionally creates minute air bubbles
R. Increases rate of setting or early hardening
S. Provides required workability with reduced water, or higher workability at the same water
Which matching is correct?
1. Accelerator
2. Retarder
3. Water reducer
4. Air-entraining admixture
P. Delays setting
Q. Intentionally creates minute air bubbles
R. Increases rate of setting or early hardening
S. Provides required workability with reduced water, or higher workability at the same water
Which matching is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
An accelerator corresponds to R because it increases the rate of setting, hardening or early strength development. A retarder corresponds to P because its defining function is to delay setting. A water reducer corresponds to S because it permits increased workability at unchanged water or a reduction in water for comparable workability. An air-entraining admixture corresponds to Q because it intentionally incorporates minute air bubbles into concrete. The complete correct matching is therefore 1-R, 2-P, 3-S and 4-Q, which is Option A.
వివరణ:
Question 20
ప్రశ్న 20
Consider the IS 9103 water-content performance limits for water-reduced concrete. Which comparison is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For the relevant IS 9103 performance comparison, a water-reducing admixture is limited to a maximum water content of 95 percent of the control concrete. This represents at least a 5 percent reduction under the test condition. A superplasticizing admixture used in a water-reduced mix is limited to a maximum of 80 percent of the control water, corresponding to at least a 20 percent reduction. The distinction reflects the substantially greater water-reducing capability expected from a superplasticizer. Therefore Option A is the correct comparison.
వివరణ:
Question 21
ప్రశ్న 21
In the IS 9103 high-workability evaluation, which statement correctly distinguishes normal and retarding superplasticizing admixtures with respect to loss of workability on standing?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 9103 includes workability-retention requirements for superplasticizers evaluated in a high-workability test mix. For the normal type, the slump at 45 minutes is required not to fall below the control-mix slump measured at 15 minutes. For the retarding type, the corresponding assessment extends to 2 hours, again relative to the control value at 15 minutes. This reflects the longer workability-retention function expected from the retarding type. Hence Option A correctly distinguishes the two performance requirements.
వివరణ:
Question 22
ప్రశ్న 22
A superplasticizer gives excellent initial slump at the manufacturer's nominal dosage, but the trial concrete shows severe segregation and excessive bleeding. What is the best engineering response?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A high measured slump alone does not establish that a concrete mixture is satisfactory. Severe segregation or excessive bleeding indicates instability and can lead to non-uniform hardened concrete and poor durability. The dosage, binder system, aggregate grading and compatibility should therefore be reassessed through controlled trials. Overdosage of a dispersing admixture can be one possible contributor, although the actual cause should be established rather than assumed. Option C represents the appropriate performance-based engineering decision.
వివరణ:
Question 23
ప్రశ్న 23
Which statement correctly distinguishes entrained air from undesirable entrapped air in concrete?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Entrained air is intentionally incorporated as a system of small distributed bubbles, usually through an air-entraining admixture. Entrapped air refers to unintended voids that remain in concrete because of mixing, placing or inadequate compaction. The two void systems differ in their origin, typical size distribution and engineering significance. Properly controlled entrained air can improve freeze-thaw resistance, whereas excessive entrapped air generally reflects poor consolidation and reduces concrete quality. Therefore Option A correctly distinguishes the two concepts.
వివరణ:
Question 24
ప్రశ్న 24
When an air-entraining admixture is tested specifically for air entrainment under IS 9103, the admixture quantity is selected to produce an air content within which range in the test concrete?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 9103 specifies a test condition for an admixture being evaluated specifically for air entrainment. The dosage is selected so that the test concrete contains air in the range of 3.5 to 7 percent. This range belongs to the standard's evaluation procedure and should not be interpreted as a universal field air-content requirement for every concrete structure. Required field air content depends on factors such as exposure, aggregate size and the applicable project specification. Consequently Option C is the correct code-based range for the stated test condition.
వివరణ:
Question 25
ప్రశ్న 25
A pumped reinforced-concrete mix has a strict maximum water-cement ratio and requires a substantial increase in workability without sacrificing that ratio. Which admixture is the most direct choice?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A superplasticizer is specifically capable of producing very high workability or a large reduction in water content for a given workability. It is therefore well suited to a pumped mix that must remain highly workable while respecting a maximum water-cement ratio. An accelerator principally addresses setting and early hardening, while a retarder principally delays setting. Air entrainment may improve workability to some extent but is not the direct substitute for high-range water reduction in the stated problem. Thus Option A is the best engineering selection.
వివరణ:
Question 26
ప్రశ్న 26
Consider the following statements about concrete admixtures:
1. IS 9103 covers accelerating, retarding, water-reducing, air-entraining and superplasticizing admixtures.
2. Once an admixture complies with IS 9103, its effect on durability and reinforcement corrosion need not be considered.
3. Two admixtures that are individually satisfactory may be assumed compatible without interaction data.
4. Water contributed by a liquid admixture may need to be included when controlling the total batch water and water-cement ratio.
Which statements are correct?
1. IS 9103 covers accelerating, retarding, water-reducing, air-entraining and superplasticizing admixtures.
2. Once an admixture complies with IS 9103, its effect on durability and reinforcement corrosion need not be considered.
3. Two admixtures that are individually satisfactory may be assumed compatible without interaction data.
4. Water contributed by a liquid admixture may need to be included when controlling the total batch water and water-cement ratio.
Which statements are correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Statement 1 is correct because these five categories form the principal admixture types covered by IS 9103. Statement 2 is incorrect because IS 456 requires admixtures not to impair durability, form harmful compounds or increase the risk of reinforcement corrosion. Statement 3 is incorrect because interaction and compatibility must be assessed when two or more admixtures are used simultaneously. Statement 4 is correct because water introduced through a liquid admixture must be considered where it contributes to the effective batch-water quantity. Therefore only Statements 1 and 4 are correct, making Option A the unique answer.
వివరణ:
Answer Key సమాధానాల పట్టిక
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Question 1 ప్రశ్న 1Answer: A. IS 9103:1999 సమాధానం: A.
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Question 2 ప్రశ్న 2Answer: B. A material added immediately before or during mixing to modify one or more properties of concrete or mortar, other than the basic constituents and specified additions excluded by the definition సమాధానం: B.
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Question 3 ప్రశ్న 3Answer: C. It increases the rate of hydration, shortens setting time or increases the rate of hardening and strength development. సమాధానం: C.
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Question 4 ప్రశ్న 4Answer: B. Accelerating admixture సమాధానం: B.
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Question 5 ప్రశ్న 5Answer: A. Retarding action సమాధానం: A.
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Question 6 ప్రశ్న 6Answer: A. It can increase workability without increasing water, or maintain workability with a reduced quantity of water. సమాధానం: A.
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Question 7 ప్రశ్న 7Answer: C. 190 kg/m³ సమాధానం: C.
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Question 8 ప్రశ్న 8Answer: C. 144 kg/m³ సమాధానం: C.
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Question 9 ప్రశ్న 9Answer: B. Use the superplasticizer to increase workability without a corresponding increase in mixing water. సమాధానం: B.
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Question 10 ప్రశ్న 10Answer: A. It is intended to prolong workability retention and retard setting in addition to providing superplasticizing action. సమాధానం: A.
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Question 11 ప్రశ్న 11Answer: A. It deliberately incorporates numerous minute air bubbles and can improve resistance to freezing and thawing. సమాధానం: A.
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Question 12 ప్రశ్న 12Answer: A. Compressive strength generally tends to decrease. సమాధానం: A.
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Question 13 ప్రశ్న 13Answer: B. The manufacturer should declare chloride content, and relatively high chloride levels are of particular concern for corrosion of prestressing steel. సమాధానం: B.
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Question 14 ప్రశ్న 14Answer: A. Workability, compressive strength and slump loss సమాధానం: A.
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Question 15 ప్రశ్న 15Answer: C. 3.36 kg/m³ సమాధానం: C.
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Question 16 ప్రశ్న 16Answer: B. 177 kg/m³ సమాధానం: B.
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Question 17 ప్రశ్న 17Answer: A. Relative density is checked for each drum and chloride content is independently tested for each batch before acceptance. సమాధానం: A.
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Question 18 ప్రశ్న 18Answer: B. Obtain data or conduct suitable trials to assess their interaction and compatibility before use. సమాధానం: B.
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Question 19 ప్రశ్న 19Answer: A. 1-R, 2-P, 3-S, 4-Q సమాధానం: A.
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Question 20 ప్రశ్న 20Answer: A. Water reducer: maximum 95 percent of control water; superplasticizer: maximum 80 percent of control water సమాధానం: A.
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Question 21 ప్రశ్న 21Answer: A. For the normal type, the slump at 45 minutes is compared with the control slump at 15 minutes, whereas the retarding type is assessed at 2 hours against the control slump at 15 minutes. సమాధానం: A.
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Question 22 ప్రశ్న 22Answer: C. Reassess dosage, mixture proportions and compatibility through trials before approving the admixture system. సమాధానం: C.
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Question 23 ప్రశ్న 23Answer: A. Entrained air consists of intentionally produced small, distributed bubbles, whereas entrapped air generally consists of larger unintended voids associated with mixing and insufficient compaction. సమాధానం: A.
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Question 24 ప్రశ్న 24Answer: C. 3.5 to 7.0 percent సమాధానం: C.
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Question 25 ప్రశ్న 25Answer: A. A superplasticizing admixture సమాధానం: A.
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Question 26 ప్రశ్న 26Answer: A. 1 and 4 only సమాధానం: A.