She didn't know________. A.what she could do it

B.what to do it
C.what she can do
D.how to do it

选择D吧 她不知道怎样做（它）。
一般这一类的是这么记的。 she did't know what to do .do 后面没有宾语it 那么用what。其实what就是do的宾语。（她不知道做什么）。
还有一种是就是这个选择she didn't how to do it. do后面有宾语it，就选择how表示方式，怎么做的意思。（她不知道怎么做这件事）

另外 what to do 和how to do 都是疑问词+to do （动词不定式）的一个用法。

D. A.B后去掉it 就对了，C时态不对，应该是what she could do.所以选D。 通常用法是what to do How to do +宾语

b

选C。 A、B、D选项都要去掉it。。 She didn't know what she could do. 她不知道怎么办。 望采纳，祝开心~！

She didn't know________. A.what she could do it B.what to do it C.what she can do D.how to do it 选项是D

D 宾语从句 可以用 What to do How to do How to do it What she could do 这四种情况