单项选择题

A new study on birds' sleep has revealed that______.

A．half-brain sleep is found in a wide variety of birds
B．halt-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

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单项选择题

While sleeping, some water mammals tend to keep half awake in order to______.

A．alert themselves to the approaching enemy
B．emerge from water now and then to breathe
C．be sensitive to the ever-changing environment
D．avoid being swept away by rapid currents

单项选择题

The new trend in artificial intelligence research stems from

A．the shift of the focus of study on to the recognition of the shapes of objects
B．the belief that human intelligence cannot be duplicated with logical, step-by-step programs
C．the aspirations of scientists to duplicate the intelligence of a ten-month-old child
D．the efforts made by scientists in the study of the similarities between transistors and brain cells