问题描述：
I don't know when I can post this letter .
I don't know when I can post this letter.(改为同义句）
I don't know ( ) ( ) ( ）this letter.
I don't know when I can post this letter.(改为同义句）
I don't know ( ) ( ) ( ）this letter.
问题解答：
我来补答展开全文阅读