Question

what they have done __useful to the people

A are considered B is considered C were considered D will be considered
什么意思？选哪个`为什么。。

Answer 1

答案：B

翻译：他们的所作所为被认为是对人们有益的。

解释：what引导从句作主语，谓语动词用单数，排除AC，答案D 用的是一般将来时，根据句意，排除。

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Answer 2

选b. consider sth.+形容词，"认为某事怎样怎样"如
I consider him dishonest 我认为他不诚实。
变成被动语态就是： He is considered dishonest.
这句的意思是：他们的行为被认为是对人民有用的。
what they have done 是主语从句，当作第三人称，所以要用is considered.
D 是将来时态，有时也可以用

Answer 3

B，what they have done他们所做的，为单数， 整体为主语，并用了现在完成时