Though sucking zinc lozenges has been promoted as a treatment for the common cold, research has revealed no consistent effect. Recently, however, a zinc gel applied nasally has been shown to greatly reduce the duration of colds. Since the gel contains zinc in the same form and concentration as the lozenges, the greater effectiveness of the gel must be due to the fact that cold viruses tend to concentrate in the nose, not the mouth.

In order to evaluate the argument, it would be most helpful to determine which of the following?

A. Whether zinc is effective only against colds, or also has an effect on other virally caused diseases

B. Whether there are remedies that do not contain zinc but that, when taken orally, can reduce the duration of colds

C. Whether people who frequently catch colds have a zinc deficiency

D. Whether either the zinc gel or the lozenges contain ingredients that have an impact on the activity of the zinc

E. Whether the zinc gel has an effect on the severity of cold symptoms, as well as on their duration

I am facing problems deciding between B and D.
Please can you help explain your approach.
Thanks.

Samy,

I'm not loving any of the answer choices and am confident that this question as written would not show up on an Official GMAT. However, if I were forced to answer, I would choose D. The conclusion of the arg is that the greater effectiveness of the gel must be due to the fact that cold viruses tend to concentrate in the nose, not the mouth. To evaluate this conclusion, we must assess additional information over whether this is truly why the gel is more effective. Choices A and C are outside the scope of the argument, and answer choice E is an incorrect "attractive distractor," as the argument discusses the duration of colds but never mentions the severity of cold symptoms. Finally, choice B can be eliminated as it does not shed any insight on the relationship between the zinc lozenges and the zinc gel.

Choice D, the "best" answer (best of the bad!), evaluates whether some inherent difference between the lozenges and the gel could influence how effective each one is. This would provide addition insight into whether a factor other than the location of where each product is applied is responsible for the difference in effectiveness between the two products.

-dan

Thanks Dan.
Clear on that one now.