There is no night on. They _____ be at home. A can’t B mustn’t C needn’t D shouldn’t
Although I often send e-mails to Tom, I have never seen him _____________.
The police asked him to _________what he had seen.
The number of people in the party _____fifty, but a number of them ____ absent for different reasons.
He asked us ________ we saw the lost cat or not.
After the exam, my teacher told me that failure ____ the mother of success.