PrepTest 153, Section 2, Question 10

What we’re looking for

Working the answers

• A
  Correct

  This is a little stronger than the simple comparison I predicted: it says the common form eliminates nicotine most rapidly. But the task asks what would explain the pattern if true. We are allowed to add this fact; we do not have to prove it from the smoking pattern alone.

  With A, the explanation is complete. Smokers with the common form eliminate nicotine fastest, so they crave another cigarette sooner. Smokers with other forms eliminate it more slowly, so their next craving comes later. The new fact connects the enzyme difference to the stated difference in smoking.

• B

  We are comparing smokers with one form of the enzyme to smokers with other forms. People who do not smoke are outside that comparison. Knowing that many people with the rarest form are nonsmokers does not explain why the smokers with the common form tend to smoke more.

• C

  Neither group in the observed comparison lacks the enzyme. Both make it; they make different forms. Slow nicotine elimination in people who make none does not tell us which of the existing forms works faster.

• D

  Quantity and form are different. Two people could make the same amount of the enzyme while making different forms of it. D would not explain a difference between them. And even if producing more enzyme speeds elimination, we have not been told that people with the common form produce more of it. We still lack a connection to the groups whose smoking differs.

• E

  The enzyme could perform several other functions, but that alone would not explain the smoking pattern. We need a difference that connects the common form to faster nicotine elimination or an earlier craving. E supplies neither.