Experiment of this kind _____ in both the U.S. and Europe well before the Second World War. [ ]A. ha

题目简介

Experiment of this kind _____ in both the U.S. and Europe well before the Second World War. [ ]A. ha

题目详情

Experiment 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
题型:单选题难度:偏易来源:北京高考真题

答案

D

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