【单选题】Birds are literally half-asleep-with one brain hemisphere alert and the other sleeping, according to a new study of sleeping ducks. Earlier studies have documented half-brain sleep in a wide range of ...
A.
half-brain sleep is found in all kinds of birds
B.
half-brain sleep is characterized by accelerated brain waves
C.
birds can control their half-brain sleep consciously
D.
birds always sleep with the whole of their brain at rest