Which of the following statements supports the "preserve and protect" hypothesis of sleep?

A) People tend to require more sleep after a hard day of work.
B) Sleep deprivation can lead to impaired cognitive abilities.
C) Jet lag is usually worse when traveling east than it is when traveling west.
D) Many small animals sleep during the day, when they could be easily seen by a predator.

Answer: D
Rationale: The preserve and protect hypothesis suggests two more adaptive functions of sleep: preserving energy and protecting the individual organism from harm. To support this hypothesis, researchers cite that the animals most vulnerable to predators sleep in safe hideaways and during the time of day when they are most susceptible.