Question

1.No one knows___

A.what he is writing about
B.whose he writing to
C.whom he is writing
D.that he is writing with

Answer 1

为你解答。
No one knows （A、what he is writing about）.
没人知道他正在写什么。
解释：括号中填的部分是个宾语从句。其他三项都有问题，具体分析如下---
B.whose he writing to：疑问词错，应该是who（whom）。
C.whom he is writing：不完整，缺少介词to，应该为writing to。
D.that he is writing with：疑问词错，that应该改为what。

Answer 2

　　A 该句中，No one knows what he is writing about.里的what he is writing about是宾语从句，从句必须采用陈述句语序，全句意思为：没有人知道他写作的内容。

Answer 3

应该选择A

Answer 4

选B,what引导宾语从句