题目内容
（请给出正确答案）
[主观题]
It is important us the balance of nature. A.for…to keepB.of…to keepC.for
It is important us the balance of nature.
A.for…to keep
B.of…to keep
C.for…keeping
D.of…to have kept
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A.wouldn’t you
B.didn’t he
C.weren’t you
D.didn’t you
