It was in 1990 ______ the medicine was tested on human patients.A．sinceB．thatC．b_刷题宝

题干

It was in 1990 ______ the medicine was tested on human patients.

A．since

B．that

C．before

D．when

上一题下一题 0.64难度单项选择更新时间:2013-04-28 10:42:14

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