Many animals, including humans, must sleep, and sleep is known to have a role in everything from healing injuries to encoding information in long-term memory. But some scientists claim that, from an evolutionary standpoint, deep sleep for hours at a time leaves an animal so vulnerable that the known benefits of sleeping seem insufficient to explain why it became so widespread in the animal kingdom. These scientists therefore imply that __________

Which choice most logically completes the text?

Question

Accepted Answer

prolonged deep sleep is likely advantageous in ways that have yet to be discovered.

Answer

most traits perform functions that are hard to understand from an evolutionary standpoint.

Answer

it is more important to understand how widespread prolonged deep sleep is than to understand its function.

Answer

many traits that provide significant benefits for an animal also likely pose risks to that animal.