Critical Reasoning

A study of expectant mothers suggests that thin women can significantly increase their chances of bearing bigger babies by taking zinc supplements during pregnancy. Three hundred women who took 25 milligram zinc supplements starting with the 19th week of pregnancy were compared to 250 women who took placebos. All the women also took a multivitamin-mineral supplement containing no zinc. Babies born to the zinc group weighed five ounces more on average with the greatest gain among thin women; for example, women in the zinc group who were 5'4'' tall and weighed under 110 pounds had babies one pound heavier, on average, than those born to similar-sized women in the placebo group.

The conclusion drawn in the passage above depends on which of the following assumptions?

A.Zinc found in natural sources, such as sea food, nuts and milk, is not as effective as supplements in increasing a pregnant woman's chances of bearing larger babies.

B.The first 18 weeks of pregnancy did not play a significant role in the result of the study.

C.Zinc supplements have little or no effect on the size of babies born to taller, heavier mothers.

D.Thin women who take more than 25 milligrams of zinc daily will give birth to even larger infants.

E.Zinc supplements have a greater effect on the size of babies born to thin women because women have less zinc stored in their bodies.

Choice is (B)

See my explanation:

(A)Every pregnant women can take that and this is not a factor for the experiment.
(B)CORRECT ASSUMPTION...the experiment started from 19th week. The assumption is that last 18 weeks haven't contributed much to each group specially
(C)Not true ...on an average 5 ounces higher than placebo taker
(D)This assumption can not lead to the conclusion
(E)This doesn't lead to the conclusion

I think OA should be A.

Can anyone tell why A is wrong?

mysseo, Are you sure that B is the OA. Answer choice B looks more an Inference than an Assumption. Also negating it, does not affect the conclusion. None of the answer choices look good to me..

A is incorrect because it does not affect the conclusions validity that thin women can significantly increase their chances of larger babies by taking zinc supplements. Adding other zinc sources would not make the conclusion valid.

Agree with B.
It says initial conditions before the start of the experiment should be almost same.

user12331

OA is B. It was Kaplan CAT. IMO was A so I got it wrong on the test. Kaplan's explanation for A is out of scope. The source of the zinc is never addressed by the author. I am confused about out of scope and assumption. Sometimes, I thought it is out of scope but it is assumption.