Critical Reasoning

Two groups of laboratory mice were injected with cancerous cells. One group’s cages were rotated in a disorienting manner. Two-thirds of these mice developed cancers. One-tenth of the mice in stationary cages developed cancers. The researchers concluded that stress enhances the development of cancer in laboratory mice.
The researchers’ conclusion logically depends on which of the following assumptions?
(A) Rotating the cages in disorienting manner produced stress in the mice in those cages.
(B) The injections given to the two groups of mice were not of equal strength.
(C) Injecting the mice with cancerous cells caused stress in the mice.
(D) Even without the injections the mice in the rotated cages would have developed cancers.
(E) Even the rotation of cages in a manner that is not disorienting is likely to produce stress in mice in those cages.


i found the answer to be B but i can someone explain me the logic?

i like A

premise: injection+disorienting rotation causes more cancer than injection+no rotation.

conclusion: stress=>enhances developement of cancer

A. correct, IMO. negate: if disorienting rotation produces no stress, then development of cancer cannot be enhanced in the rotated cage-argument falls apart.

B. negate: if injections were of equal strength, it singles out disoriented rotation as cause of enhancement of cancer. supports the argument. eliminate

C. if injections caused stress, then there would have been equal developemt of cancer in both cages. eliminate

D. says injection does not cause cancer. irrelevant as it doesnt talk about stress and doesnt affect the conclusion

E. non-disorienting rotation is out of scope.

Answer should be A.

arghya05 wrote:Two groups of laboratory mice were injected with cancerous cells. One group’s cages were rotated in a disorienting manner. Two-thirds of these mice developed cancers. One-tenth of the mice in stationary cages developed cancers. The researchers concluded that stress enhances the development of cancer in laboratory mice.
The researchers’ conclusion logically depends on which of the following assumptions?
(A) Rotating the cages in disorienting manner produced stress in the mice in those cages.
(B) The injections given to the two groups of mice were not of equal strength.
(C) Injecting the mice with cancerous cells caused stress in the mice.
(D) Even without the injections the mice in the rotated cages would have developed cancers.
(E) Even the rotation of cages in a manner that is not disorienting is likely to produce stress in mice in those cages.


i found the answer to be B but i can someone explain me the logic?

This question is too much vague. Two groups (were they of equal strength?) were injected with cancer cells. If we assume that two groups were of equal strength and cancer cell injections are also of equal numbers (which opposes choice "B"), then only possibility that causes stress in mice is disoriented rotation of cage ( choice "A").
I second all of you above, A should be the answer

I am leaning more towards A, but I'm not sure about it.