Question

To make our city more beautiful, rubbish ________ into the river.

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A．needn't be thrown

B．mustn't be thrown

C．can't throw

D．may not throw

Answer 1

答案：B
解析：

这是含有情态动词的被动语态．首先应排除C和D，因为它们是主动语态；含有情态动词的被动语态的构成应该是：“情态动词＋be＋及物动词的过去分词”，needn't是“不必”＝don't have to; mustn't是“禁止，不准”之意．故答案选B．