题目内容
Wind power is an ancient source of energy ______________we may return in the near future.
[ ]
A. on which
B. by which
C. to which
D. from which
B. by which
C. to which
D. from which
C
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Wind power is an ancient source of energy we may return in the near future.
A.on which | B.by which | C.to which | D.from which |