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。