单项选择题

Scientists say it may be five or six years （）this medicine is tested on human beings.

A．since
B．before
C．after
D．when

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单项选择题

With larger numbers of graduates than ever before, just having a degree will no longer be enough to make you （）in the crowd.

A．stand up
B．stand by
C．stand for
D．stand out

单项选择题

（）the obvious differences in size and population, the states of America have many things（） common.

A．Although; on
B．Though; in
C．Despite; in
D．Because of; on

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