Experiments of this kind _______in both
题型:选择题
问题:
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
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