问题补充:
It was in 1990 the medicine was tested on human patients.
A. since
B. that
C. before
D. when
答案:
A. since
(答案→)B. that
C. before
D. when
解析:考查强调句型。强调句型的基本结构为It is/was被强调成分that/who其它成分;其最大的特点就是去掉it is/was…that/who…句子仍然成立。要注意强调句型能强调除谓语动词以为的所有的句子成分。本题中强调的是时间状语in 1990;句意:就是在1990年这种药物在人类的病人身上测试的。故B正确。