We students should treasure the short senior school’s study life of three years. Once ________, the opportunity can’t get back.
| A．losing | B．was lost | C．lost | D．being lost |
Everyone _____ do his best for the modernizations of our country.
| A．can | B．may | C．should | D．might |
31. He _____ have come here yesterday, but he didn’t.
| A．could | B．should | C．ought to | D．all the above |
He ought to win the first prize, _____ he?
| A．oughtn’t | B．shouldn’t | C．mustn’t | D．both A and B |
I missed the last bus, so I _____ go home on foot.
| A．must | B．have to | C．may | D．had to |
I got up early that morning, but I _____ so because I had no work to do.
| A．mustn’t have done | B．didn’t need to do | C．needn’t have done | D．can’t have done |