难度:★ 考点:情态动词
1. School students ________ smoke because it is against the school rules.
A. needn't B. couldn't C. won't D. mustn't
2. --Have you heard that some bad thing would happen in 2012?
--Don't worry! The news be true.
A. mustn't B. may not C. needn't
3. You look tired, you must________.
A. stops to work B. shop working C. stop to work D. stopped working
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