问题

Experiments 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

正确答案是：

同类题型

Could you tell me ______ yesterday–I’m sorry, boss, My car was broken on my way here.

What do you know about Darwin after he returned from the trip by sea?-Well, he got married and ________ down to live in London．[ ]

The shoes were worn out, what’s more, they aren’tworth _____.

1—Would you like to drinksome orange juice?— Thanks. ,but I have drunk a lot of tea.

The watch ________ I paid 50 dollars was stolen by the thief.