These machines must ______ before they are used.

admin2009-08-17 36

问题 These machines must ______ before they are used.

选项 A、check
B、be checked
C、are checked

答案B

解析仍然是考查被动语态，注意must 是情态动词，后面应接动词原形be。

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公共英语一级笔试

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