Alice fixed her eyes upon Bob, there was an expression __ that he could not understand.
| A．in it | B．on them | C．in them | D．on it |
Let’s clean our classroom, _____?
| A．will you | B．don’t we | C．shall we | D．do you |
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 |