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