Scientists say it may be five or six years _______ it is possible to test this medicine on human patients.
| A．since | B．after | C．before | D．when |
It was in 1969 ______ two Americans went to the moon by spaceship.
| A．that | B．before | C．when | D．Since |
—What ________ an important part in their lives?
—Friends.
| A．plays | B．takes | C．makes | D．Acts |
He wouldn’t leave the TV set, ______ he was going to have an important exam the next day.
| A．even so | B．even if | C．as though | D．as if |
As soon as she saw her boyfriend, she ________ crying.
| A．burst into | B．broke out | C．burst out | D．broke in |
—May I ask a question after class，Sir?
—, but not during my lunch break.
| A．I am sorry | B．Anytime | C．Go ahead | D．Certainly |