单项选择题

An ignorant farmer will make the land poorer______.

A．ff he lets dead leaves decay in the soil by themselves
B．if he makes the humus decrease after taking away his crops
C．by clearing away all the dead leaves
D．by burning waste plant material lying about

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热门试题

单项选择题

We can learn from the passage that the tired land has fully recovered ______.

A．when grasses and other plants appear again
B．when the treatment is given by nature alone
C．after it has been lying idle for ten years
D．after grasses and other plants have decayed again

单项选择题

It is implied that a modem farmer cannot simply move to another place when his field has become tired. This is because ______.

A．the production power of a new field is not higher than that of an old one
B．it takes a farmer more than ten years to cultivate a new field
C．the population of the world has increased rapidly
D．there will be too many grasses in a new field to grow crops