Humankind would not have survived, as it clearly has, if our ancestors

Question

Humankind would not have survived, as it clearly has, if our ancestors had not been motivated by the desire to sacrifice themselves when doing so would ensure the survival of their children or other close relatives. But since even this kind of sacrifice is a form of altruism, it follows that our ancestors were at least partially altruistic.

Which one of the following arguments is most similar in its reasoning to the argument above?

(A) Students do not raise their grades if they do not increase the amount of time they spend studying. Increased study time requires good time management. However, some students do raise their grades. So some students manage their time well.

(B) Organisms are capable of manufacturing their own carbohydrate supply if they do not consume other organisms to obtain it. So plants that consume insects must be incapable of photosynthesis, the means by which most plants produce their carbohydrate supplies.

(C) If fragile ecosystems are not protected by government action their endemic species will perish, for endemic species are by definition those that exist nowhere else but in those ecosystems.

(D) The natural resources used by human beings will be depleted if they are not replaced by alternative materials. But since such replacement generally requires more power, the resources used to create that power will become depleted.

(E) Public buildings do not harmonize with their surroundings if they are not well designed. But any well-designed building is expensive to construct. Thus, either public buildings are expensive to construct or else they do not harmonize with their surroundings.

GMAT0010 · Answer

Hi,
Could you kindly explain why A is correct and why E is incorrect ?

peanuts · Answer

Humankind would not have survived, as it clearly has, if our ancestors had not been motivated by the desire to sacrifice themselves when doing so would ensure the survival of their children or other close relatives. But since even this kind of sacrifice is a form of altruism, it follows that our ancestors were at least partially altruistic.

Analysis: Not A if B not do C. C is a kind of D, so B is partially D

Which one of the following arguments is most similar in its reasoning to the argument above?

(A) Students do not raise their grades if they do not increase the amount of time they spend studying. Increased study time requires good time management. However, some students do raise their grades. So some students manage their time well.
 Not A if B do not do C. C requires good time management. Some A, so some B manage time well. Best of the five

(B) Organisms are capable of manufacturing their own carbohydrate supply if they do not consume other organisms to obtain it. So plants that consume insects must be incapable of photosynthesis, the means by which most plants produce their carbohydrate supplies.
 A if not B. So D must not A. WRONG

(C) If fragile ecosystems are not protected by government action their endemic species will perish, for endemic species are by definition those that exist nowhere else but in those ecosystems.
 If not A, B will happen, because B is defined as C. WRONG

(D) The natural resources used by human beings will be depleted if they are not replaced by alternative materials. But since such replacement generally requires more power, the resources used to create that power will become depleted.
 A will be depleted if A not replaced by B. But since B requires C, A will become depleted. WRONG

(E) Public buildings do not harmonize with their surroundings if they are not well designed. But any well-designed building is expensive to construct. Thus, either public buildings are expensive to construct or else they do not harmonize with their surroundings. 
 Not A if B are not C. C is expensive. Thus, either B is expensive or else A. The stem doesn't include the A at the end. So WRONG

VerbalBot · Answer

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Humankind would not have survived, as it clearly has, if our ancestors

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