Critical Reasoning

Birds need so much food energy to maintain their body temperatures that some of them spend most of their time eating. But a comparison of a bird of a seed-eating species to a bird of a nectar-eating species that has the same overall energy requirement would surely show that the seed-eating bird spends more time eating than does the nectar-eating bird, since a given amount of nectar provides more energy than does the same amount of seeds
The argument relies on which one of the following questionable assumptions
(A) Birds of different species do not generally have the same overall energy requirements as each other
(B) The nectar-eating bird does not sometimes also eat seeds
(C) The time it takes for the nectar-eating bird to eat a given amount of nectar is not longer than the time it takes the seed-eating bird to eat the same amount of seeds
(D) The seed-eating bird does not have a lower body temperature than that of the nectar-eating bird
(E) The overall energy requirements of a given bird do not depend on factors such as the size of the bird, its nest-building habits; and the climate of the region in which it lives

OA is C.

How can I do this CR question? Can someone help me.

Vincen wrote:Birds need so much food energy to maintain their body temperatures that some of them spend most of their time eating. But a comparison of a bird of a seed-eating species to a bird of a nectar-eating species that has the same overall energy requirement would surely show that the seed-eating bird spends more time eating than does the nectar-eating bird, since a given amount of nectar provides more energy than does the same amount of seeds

The argument relies on which one of the following questionable assumptions

(A) Birds of different species do not generally have the same overall energy requirements as each other
(B) The nectar-eating bird does not sometimes also eat seeds
(C) The time it takes for the nectar-eating bird to eat a given amount of nectar is not longer than the time it takes the seed-eating bird to eat the same amount of seeds
(D) The seed-eating bird does not have a lower body temperature than that of the nectar-eating bird
(E) The overall energy requirements of a given bird do not depend on factors such as the size of the bird, its nest-building habits; and the climate of the region in which it lives.

Premise: A given amount of nectar provides more energy than does the same amount of seeds.
Conclusion: The seed-eating bird spends more time eating than does the nectar-eating bird.

Apply the NEGATION TEST.
When the correct answer choice is negated, the conclusion will be invalidated.

C, negated:
The time it takes for the nectar-eating bird to eat a given amount of nectar is longer than the time it takes the seed-eating bird to eat the same amount of seeds.
Here, the nectar-eating bird takes LONGER TO EAT than the seed-eating bird, invalidating the conclusion that the seed-eating bird spends more time eating than does the nectar-eating bird.
Since the negation of C invalidates the conclusion, C is an assumption: a statement that MUST BE TRUE for the conclusion to hold.

The correct answer is C.

GMATGuruNY wrote:

Vincen wrote:Birds need so much food energy to maintain their body temperatures that some of them spend most of their time eating. But a comparison of a bird of a seed-eating species to a bird of a nectar-eating species that has the same overall energy requirement would surely show that the seed-eating bird spends more time eating than does the nectar-eating bird, since a given amount of nectar provides more energy than does the same amount of seeds

The argument relies on which one of the following questionable assumptions

(A) Birds of different species do not generally have the same overall energy requirements as each other
(B) The nectar-eating bird does not sometimes also eat seeds
(C) The time it takes for the nectar-eating bird to eat a given amount of nectar is not longer than the time it takes the seed-eating bird to eat the same amount of seeds
(D) The seed-eating bird does not have a lower body temperature than that of the nectar-eating bird
(E) The overall energy requirements of a given bird do not depend on factors such as the size of the bird, its nest-building habits; and the climate of the region in which it lives.

Premise: A given amount of nectar provides more energy than does the same amount of seeds.
Conclusion: The seed-eating bird spends more time eating than does the nectar-eating bird.

Apply the NEGATION TEST.
When the correct answer choice is negated, the conclusion will be invalidated.

C, negated:
The time it takes for the nectar-eating bird to eat a given amount of nectar is longer than the time it takes the seed-eating bird to eat the same amount of seeds.
Here, the nectar-eating bird takes LONGER TO EAT than the seed-eating bird, invalidating the conclusion that the seed-eating bird spends more time eating than does the nectar-eating bird.
Since the negation of C invalidates the conclusion, C is an assumption: a statement that MUST BE TRUE for the conclusion to hold.

The correct answer is C.

Dear Mitch,

If I negate D:

The seed-eating bird has a lower body temperature than that of the nectar-eating bird

If the body lower the seed-eating bird will spend less time eating , invalidating the the conclusion.

If I negate E:
The overall energy requirements of a given bird depend on factors such as the size of the bird, its nest-building habits; and the climate of the region in which it lives.
This means the factors that can affect the time of eating, invalidating the conclusion. In some Assumption questions, we assume no other factors in place to validate the conclusion.

Can you help with above ?

Mo2men wrote:

GMATGuruNY wrote:

Vincen wrote:Birds need so much food energy to maintain their body temperatures that some of them spend most of their time eating. But a comparison of a bird of a seed-eating species to a bird of a nectar-eating species that has the same overall energy requirement would surely show that the seed-eating bird spends more time eating than does the nectar-eating bird, since a given amount of nectar provides more energy than does the same amount of seeds

The argument relies on which one of the following questionable assumptions

(A) Birds of different species do not generally have the same overall energy requirements as each other
(B) The nectar-eating bird does not sometimes also eat seeds
(C) The time it takes for the nectar-eating bird to eat a given amount of nectar is not longer than the time it takes the seed-eating bird to eat the same amount of seeds
(D) The seed-eating bird does not have a lower body temperature than that of the nectar-eating bird
(E) The overall energy requirements of a given bird do not depend on factors such as the size of the bird, its nest-building habits; and the climate of the region in which it lives.

Premise: A given amount of nectar provides more energy than does the same amount of seeds.
Conclusion: The seed-eating bird spends more time eating than does the nectar-eating bird.

Apply the NEGATION TEST.
When the correct answer choice is negated, the conclusion will be invalidated.

C, negated:
The time it takes for the nectar-eating bird to eat a given amount of nectar is longer than the time it takes the seed-eating bird to eat the same amount of seeds.
Here, the nectar-eating bird takes LONGER TO EAT than the seed-eating bird, invalidating the conclusion that the seed-eating bird spends more time eating than does the nectar-eating bird.
Since the negation of C invalidates the conclusion, C is an assumption: a statement that MUST BE TRUE for the conclusion to hold.

The correct answer is C.

Dear Mitch,

If I negate D:

The seed-eating bird has a lower body temperature than that of the nectar-eating bird

If the body lower the seed-eating bird will spend less time eating , invalidating the the conclusion.

If I negate E:
The overall energy requirements of a given bird depend on factors such as the size of the bird, its nest-building habits; and the climate of the region in which it lives.
This means the factors that can affect the time of eating, invalidating the conclusion. In some Assumption questions, we assume no other factors in place to validate the conclusion.

Can you help with above ?

The passage compares a bird of a seed-eating species to a bird of a nectar-eating species that HAS THE SAME OVERALL ENERGY REQUIREMENTS.
Thus, it is a PREMISE that the birds being compared all require the same amount of energy.
The negations of D and E attempt to weaken this premise.
A premise is a FACT: it cannot be weakened.
Any answer choice whose negation seems to weaken a premise is WRONG.
Eliminate D and E.