It ________ be the vocabulary that caused you the problem in the exercise because you know a lot of words.
A．may B．couldn't
C．should D．needn't
—You needn't take an umbrella. It isn't going to rain.
—Well, I don't know. It ________do.
A. might B. need
C. would D. should
If we ________ a table earlier, we wouldn't be standing here in a queue.
A. have booked B. booked
C. book D. had booked
I should not have laughed if I ________ you were serious.
A．thought B．would think
C．had thought D．have thought
He ________ sleep, although he tried to, when he got on such a hunt for an idea until he had caught it.
A. wouldn't B. shouldn't
C. couldn't D. mustn't
When I was a child, I ________ watch TV whenever I wanted to.
A. should B. could
C. must D. need
