问题
选择题
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
答案
答案: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。