She looks very sad.I want to help her but I don't know____to do.A.what B.how C.where D.when选什么

She looks very sad.I want to help her but I don't know____to do.A.what B.how C.where D.when选什么
She looks very sad.I want to help her but I don't know____to do.A.what B.how C.where D.when
选什么

She looks very sad.I want to help her but I don't know____to do.A.what B.how C.where D.when选什么
B
她看起来很伤心,我想帮助她但是我不知道怎么做.

选B
他看起来很伤心，我想帮她，但不知道怎么做。我想也是B 问题答案上是A呢how to do表示怎样做 what to do表示做什么 这里只要弄懂how和what分别是什么意思就好了 但很少情况下意思可以作为怎么做来看。这样的情况下，要区分how 和what 所充当的成分。意思相同，what与how同样引导宾语从句，但在用法上有区别： what可充当宾语，故不定式后不...

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选B
他看起来很伤心，我想帮她，但不知道怎么做。

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选A。意思是：……我不知道该做什么。I don't know what to do相当于I don't know what I should do.可以看出，do的宾语只能是what，所以选A。

答案是A
详如果选择B，那就是： I don't know how to do.成分：主语（I）+谓语（don't know）+宾语从句，而how to do这个句子是不完整的，无法构成一个宾语从句，少了宾语it(指帮她这件事),完整的应为I don't know how to do it.这样就对。
选A的话，就是I don't know what to do.
what...

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答案是A
详如果选择B，那就是： I don't know how to do.成分：主语（I）+谓语（don't know）+宾语从句，而how to do这个句子是不完整的，无法构成一个宾语从句，少了宾语it(指帮她这件事),完整的应为I don't know how to do it.这样就对。
选A的话，就是I don't know what to do.
what：对行为内容表示提问，是疑问代词
what to do：做什么，what即是do的宾语，所以可以。
例：I don't know how to do it. 我不知道怎么做这件事。
I don't know what to do. 我不知道该做什么。

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