问题
Scientists say it may be fiveyears ______ it is possible to test this medicine on human patients．
A:since
B:until
C:before
D:when
B:until
C:before
D:when
正确答案是：
同类题型
This bike looks very nice. It only 150 yuan
There is little doubt in your mind that he is innocent, _______?[ ]
Something ______ when they made a birthday card.
Johnis very ——if he promises to do something he’lldo it .
Remember the first time we met—Sure. You _____________ the novel Gone With theWind in the library.