问题
选择题
Experiments of this kind ___in both the U.S and Europe well before the Second World War.
A．had conducted
B．have conducted
C．have been conducted
D．had been conducted
答案
答案：D
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，且“实验”是被“进行”，故选D。