20.It is vital that the work _______ in time. A. is done B. be done C. are done D. was done 怎么做

B
我前面填写了:be finished,道理也讲了,就是it is vital后面要用should 动词原型的虚拟语气,这里换了一个动词,那就变成be done,举一反三才能学好英语.

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