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

The experiment with the dove indicated that ______.

A．birds can fly in the same direction as that taken by their cousins
B．a bird that has been caged will not fly long distances
C．some birds seem to follow the stars when they fly at night
D．a bird having spent its lifetime in a cage has to be taught how to navigate

单项选择题

The word hazard in the last paragraph most probably means ______.

A．danger
B．enemy
C．frightening
D．punishment