题目内容
Experiments of this kind in both the U.S.and Europe well before the Second World War.
| A.have conducted | B.have been conducted |
| C.had conducted | D.had been conducted |
D
本题考查时态。根据句中时间状语before the Second World War可知用过去完成时,由于experiments与conduct为被动,故选D。
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