Experiments of this kind _______ in both the U.S. and Europe well before the Second World War.（2011北京卷21）
| A．have conducted |
| B．have been conducted |
| C．had conducted |
| D．had been conducted |
相关试题
Bill suggesteda meeting on what to do for the Shanghai Expo during the vacation.
| A． | having held | B． | to hold | C． | holding | D． | hold |
During the period of recent terrorist activities, people _____ not to touch and unattended bag.
| A．had always been warned | B．were always being warned |
| C．are always warning | D．always warned |
It is immediately clear ____ the financial crisis will soon be over.
| A．since | B．what | C．when | D．whether |
Hearing the dog barking fiercely, away.
| A． | fleeing the thief | B． | was fleeing the thief |
| C． | the thief was fleeing | D． | fled the thief |
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