Under laboratory conditions, fruit flies can learn to respond to odors that elicit no response from them in nature. Mutant fruit flies that cannot produce a certain enzyme are, however, incapable of such learning. These mutant flies respond to other odors just as ordinary fruit flies do. Thus it is unlikely that the enzyme’s absence impairs the fruit flies’ perception of odors, since presumably fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature. Given that many researchers believe that this enzyme is somehow involved in the process of forming memories, what the enzyme’s absence probably impairs is the fruit flies’ ability to learn.
In the argument given, the two boldfaced portions play which of the following roles?
A . The first is a conclusion drawn about one possible explanation of the phenomenon at issue; the second presents an explicit assumption that is introduced to support that conclusion.
B . The first is a hypothesis that the argument seeks to establish; the second is an alternative hypothesis, which the argument provides grounds for rejecting.
C . The first is a hypothesis that the argument seeks to establish; the second presents an explicit assumption that has been used in arguing for the position that the argument opposes.
D . The first provides evidence in support of the main conclusion of the argument; the second is a claim that has been advanced in order to undermine the force of that evidence.
E . The first is an objection that has been raised against the position adopted in the argument; the second presents an explicit assumption that is introduced in order to meet that objection.
Answer: E
Leave a Reply