eitijan wrote:Until now, only injectable vaccines against influenza have been available. Parents are reluctant to subject children to the pain of injections, but adults, who are at risk of serious complications from influenza, are commonly vaccinated. A new influenza vaccine, administered painlessly in a nasal spray, is effective for children. However, since children seldom develop serious complications from influenza, no significant public health benefit would result from widespread vaccination of children using the nasal spray.

Which of the following is an assumption on which the argument depends?

A. Any person who has received the injectable vaccine can safely receive the nasal-spray vaccine as well.

B. The new vaccine uses the same mechanism to ward off influenza as injectable vaccines do.

C. The injectable vaccine is affordable for all adults.

D. Adults do not contract influenza primarily from children who have influenza.

E. The nasal spray vaccine is not effective when administered to adults.

In assumption questions there is generally a gap between the basis of the argument and the conclusion. In this case the gap seems to be between the absence of certain benefits of the vaccine for children and an absence of benefits to public health of administering the vaccine to children.

The correct answer will be one that is consistent with the leap from absence of certain benefits for children to absence of public health benefits.

(A) This does not have to be the case.

(B) This does not have to be the case.

(C) This is trap answer that may get you if you have certain ideas in your mind, but really it is not necessary for connecting the absence of benefits for children to absence of public health benefits.

(D) This is interesting. If adults contract influenza primarily from children who have it, then preventing influenza in children would prevent it in adults as well. So an argument that says that preventing influenza in children has no public health benefits depends on the assumption that adults don't primarily contract influenza from children who have already contracted it.

(E) This could be a "sounds right" trap answer. It is irrelevant really, but if you aren't sure what is going on in the question you might pick this one because it somehow sounds right.

So only one answer choice says something that must be true in order for the argument to work.

The correct answer is D.