Qian Xuesen tried many times _________ he found the solution to the puzzle about space technology.
| A．after | B．before | C．since | D．when |
I don’t think he＿＿＿＿＿＿＿ a new bike.
| A．need to buy | B．needs buy | C．need | D．need buy |
Tom＿＿＿＿＿＿＿show his exam results to his parents.
| A．dare not | B．dared | C．dare to | D．dares not to |
Let’s clean the classroom, ＿＿＿＿＿＿＿?
| A．won’t you | B．shall we | C．do we | D．will not you |
Children＿＿＿＿＿＿＿＿in public very often.
| A．should be praised | B．shouldn’t have praised |
| C．shouldn’t have been praised | D．shouldn’t be praised |
I was really anxious about you. You＿＿＿home without a word.
| A．mustn’t leave | B．shouldn’t have left |
| C．couldn’t have left | D．needn’t leave |