The Finding That Sleep Is More Efficient in People Who

Multiple Choice

The finding that sleep is more efficient in people who regularly sleep less is a key finding because it indicates that

A) sleep-deprivation studies can indicate how much sleep people actually need only if the volunteers who are being studied are efficient sleepers to begin with.
B) sleep is a positive incentive.
C) sleep is made more efficient by reinforcements and punishments.
D) REM sleep is fundamentally recuperative.
E) sleep can be conditioned.