Question

 Experiments of this kind _______in both the U.S. and Europe well before the Second World War started.

A．have conducted                        B．have been conducted

C．had conducted                         D．had been conducted

Answer

D

【解析】

试题分析：句意：在第二次世界大战之前这种实验就在美国和欧洲做过。因为时间状语before the Second World War started.这里的谓语动词是过去式，conduct是在这个动作之前的发生的动作，故用过去完成时，又因为experiments与conduct之间是被动关系，故选D。

考点：考查动词时态的用法。