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 |
He has devoted himself __ mankind.
to benefit B. benefiting C. to benefiting D. benefited
Robert is said ____ abroad, but I don’t know what country he studied in.
| A．to have studied | B．to study | C．to  be studying |
D．to have been studying |
Wang Gang is considering buying a computer, is considered to be a great help in our work and study.
| A．as | B．which | C．that | D．what |
When we climbed up to the top of the mountain, we were all ___________.
| A．out of the breath | B．short of the breath |
| C．out of breath | D．short of breaths |
—I’ m sorry, but I didn’t mean__________ out your secret.
—But you know, letting out one’s secret means________ one’ s feelings.
| A．to let; to hurt | B．letting; hurting |
| C．to let; hurting | D．letting; to hurt |