题目内容

简述陆地生态系统里的碳循环过程。

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People in the plane can__________

A. have a good sleep
B. have some small gifts
C. buy some duty-free goods
D. go to the bar to have a drink

种内关系和种间关系的基本类型。

r对策和k对策的主要特征及优缺点。

The word “primitive”in paragraph 4 is closest in meaning to which of the folowing?

A. simple
B. very ancient
C. perfect
D. important

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