Experiments of this kind ___in both the U.S and Europe well before the Second World War. A.had condu

题目简介

Experiments of this kind ___in both the U.S and Europe well before the Second World War. A.had condu

题目详情

Experiments of this kind ___in both the U.S and Europe well before the Second World War.
A.had conductedB.have conductedC.have been conductedD.had been conducted
题型:单选题难度:中档来源:不详

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。

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