单项选择题

Experiments showed that ______.

A．birds are likely to get lost if there aren't man-made stars.
B．day-flying birds depend on the sun while night-flying birds depend on the stars
C．birds depend on the sun to guide them
D．birds depend on the stars to guide them

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热门试题

单项选择题

In total darkness, doves ______.

A．circle helplessly
B．use landmarks
C．find their way by clouds
D．fly back home

单项选择题

Under man-made stars, the bird in the cage ______.

A．tried to fly in the opposite direction of birds not caged
B．changed direction when the position of the stars was changed
C．wouldn't fly well
D．stayed where they were