单项选择题

When there is a heavy rain, trees can help to prevent floods, as they can ______

A．keep rain from falling down to soft ground
B．cause the soil to allow rainwater to sink in
C．make the topsoil stick together
D．prevent the soil from being washed away

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热门试题

单项选择题

Sooner or later the forests will disappear ______

A．if people don't stop cutting trees
B．unless a country has a plenty supply of trees
C．unless all people the importance of planting trees and the government has good system of control.
D．if man doesn't stop cutting trees carelessly

单项选择题

Two thousand years ago, a rich and powerful country met with floods and starvation because of ______

A．the soil of the country became barren
B．its empire fell
C．it cut too many trees down
D．the conquered land within its empire was poor and barren