When Peter speaks in public, he always has trouble _ the right things to say.
| A．thinking of | B．to think of | C．thought of | D．think of |
______ you do the experiment carefully, you would make discoveries others wouldn’t make.
| A．Should | B．Would | C．Could | D．Might |
We had to the match as the ground was too wet to play on.
| A．call off | B．call up | C．call out | D．call for |
It was 1995 __________ we began to develop the new computer system.
| A．when | B．which | C．since | D．that |
He is _________ to have gone abroad,for I haven’t seen him for weeks.
| A．possible | B．likely | C．probable | D．certainly |
As a teacher, I seldom give my students so difficult a problem_______ they can’t work out.
| A．that | B．as | C．if | D．in order that |