单项选择题

According to the passage,______.

A．early man did not know how to make use of trees
B．tree are not as useful now as they were in the past
C．trees were more useful in the past than they are now
D．men have always found trees useful

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热门试题

单项选择题Top soil means ______.

A．useless soil
B．soil found under the earth
C．soil on the surface of the earth
D．dry soil which is found in the desert

单项选择题According to the passage some desert areas were once ______.

A．fertile lands
B．covered by rivers
C．very cold
D．very dry and useless lands.