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A．The lifecycle of trees.
B．The number of trees.
C．The intensity of solar burning.
D．The quality of air.
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单项选择题
A．It will increase the amount of unpleasant odors from vehicles.B．It will eventually destroy the ozone layer.C．It will reduce the amount of pollutants in the air.D．It will reduce the cost of running large vehicles.
A．It will increase the amount of unpleasant odors from vehicles.
B．It will eventually destroy the ozone layer.
C．It will reduce the amount of pollutants in the air.
D．It will reduce the cost of running large vehicles.
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