PrepTest 147, Section 4, Question 1

What we’re looking for

Working the answers

• A

  This fits the general idea that cold weather slows cold-blooded animals down. But it doesn't distinguish the two movements of this chameleon's tongue. Knowing that animals are usually more active in warmth leaves the unusual extension speed unexplained.

• B

  Distance isn't speed. A tongue could travel a long way either quickly or slowly. B also doesn't explain why colder temperatures affect the inward movement much more than the outward movement. The reach of the tongue isn't the contrast we're trying to understand.

• C

  Different habitats expose the animals to different conditions, but we still need to explain what happens when the temperature falls. Simply finding chameleons in both variable and moderate climates doesn't tell us why one direction of tongue movement slows much more than the other.

• D
  Correct

  The two movements use different sources of power. Muscles pull the tongue back, so the stated effect of cold on muscle power explains why retraction slows. Extension uses stored energy in a rubber band-like sheath instead. It needn't be affected in the same way as the muscle-powered return.

  Think of the difference between pulling something with a muscle and releasing a stretched band. D gives us a reason the outward movement can remain quick even when the muscles have weakened. We don't need the tongue to be completely unaffected by cold; the passage says extension declines only a little.

• E

  This compares the chameleon's retraction muscles with those of other animals. Stronger muscles could still weaken in colder weather. More importantly, the comparison we need is extension versus retraction within this chameleon, not this animal's muscles versus another animal's muscles.