单项选择题

Why do forests in many parts of the world slowly disappear

A．New trees are not looked after properly.
B．Many trees have been cut down by man.
C．Man has not paid enough attention to planting trees.
D．All of the abov

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单项选择题

Why did the country mentioned in the passage suffer from floods and starvation

A．Because nothing remains on land except floods.
B．Because there are no longer trees to keep the rain and protect the top—soil.
C．Because too much rain sinks in and washes away the top— soil.
D．Because roots of the trees break up the soil.

单项选择题

What is the most important service of trees to man according to the passage

A．They help him make money.
B．They give him wood and other products.
C．They help him prevent droughts and floods.
D．They give him shad