[单项选择]

Birds that are literally half-asleep---with one brain hemisphere alert and the other sleeping- control which side of the brain remains awake, according to a new study of sleeping ducks.
Earlier studies have documented half-brain sleep in a wide range of birds. The brain hemi- spheres take turns sinking into the sleep stage characterized by slow brain waves. The eye con- trolled by the sleeping hemisphere keeps shut, while the wakeful hemisphere’ s eye stays open and alert. Birds also can sleep with both hemispheres resting at once.
Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end-or-the-row sleepers. Sure enough, the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction.
Also, birds dozing(打盹) at the end of the line resorted to single-hemisphere sleep, rather than total relaxation, more often than inner ducks
A. remain fascinated by them
B. remain indifferent to them
C. are ready to face up to them
D. are willing to get involved in them

[单项选择]

Birds that are literally half-asleep---with one brain hemisphere alert and the other sleeping- control which side of the brain remains awake, according to a new study of sleeping ducks.
Earlier studies have documented half-brain sleep in a wide range of birds. The brain hemi- spheres take turns sinking into the sleep stage characterized by slow brain waves. The eye con- trolled by the sleeping hemisphere keeps shut, while the wakeful hemisphere’ s eye stays open and alert. Birds also can sleep with both hemispheres resting at once.
Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end-or-the-row sleepers. Sure enough, the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction.
Also, birds dozing(打盹) at the end of the line resorted to single-hemisphere sleep, rather than total relaxation, more often than inner ducks
A. have monopolized the talk show circuit
B. appear at different times of the day
C. exploit the weaknesses in human nature
D. are targeted at different audiences

[单项选择]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 birds. The brain hemispheres take turns sinking into the sleep stage characterized by slow brain waves. The eye controlled by the sleeping hemisphere keeps shut, while the wakeful hemisphere’s eye stays open and alert. Birds also can sleep with both hemispheres resting at once.
Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end-of-the-row sleepers. Sure enough, the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction.
Also, birds dozing (打盹) at the end of the line resorted to single-hemisphere sleep, rather than total relaxation, more often than inner ducks did. Rotating 16 birds through the positions in a four-duck row, the researcher
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

[单项选择]Birds that are literally half asleep--with one brain hemisphere alert and the other sleeping --control which side of the brain remains awake, according to a new study of sleeping ducks.
Earlier studies have documented half brain sleep in a wide range of birds. The brain hemispheres take turns sinking into the sleep stage characterized by slow brain waves. The eye controlled by the sleeping hemisphere keeps shut, while the wakeful hemisphere’s eye stays open and alert. Birds also can sleep with both hemispheres resting at once.
Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end of the row sleepers. Sure enough, the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction.
Also, birds dozing at the end of the line resorted to single hemisphere sleep, rather than total relaxation, more often than inner ducks did. Rotating 16 birds t
A. half brain sleep is found in a wide variety of birds.
B. half brain sleep is characterized by slow brain waves.
C. birds can control their half brain sleep consciously.
D. birds seldom sleep with the whole of their brain at rest.

[单项选择]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 birds. The brain hemispheres take turns sinking into the sleep stage characterized by slow brain waves. The eye controlled by the sleeping hemisphere keeps shut, while the wakeful hemisphere’s eye stays open and alert. Birds also can sleep with both hemispheres resting at once.
Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end-of-the-row sleepers. Sure enough, the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction.
Also, birds dozing (打盹) at the end of the line resorted to single-hemisphere sleep, rather than total relaxation, more often than inner ducks did. Rotating 16 birds through the positions in a four-duck row, the researche
A. A．8), Siegel suggests that ______ half-brain sleep has something to do with icy weatherB. the mystery of half-brain sleep is close to being solvedC. most birds living in cold regions tend to be half sleepersD. half-brain sleep is a phenomenon that could exist among other species