Question

高中英语 单句改错求讲解

1This is the most expensive pen which I have bought.
2I will never forget the day which I first met you on the ship.
3This is all what I know about the mater.

Answer 1

1. which改成that，因为句子中出现了最高级，引导词只能用that。

2. which改成when，定语从句中缺少时间状语，所以用when

3. what改成that，因为what不能引导定语从句。（或者却掉all，也可以，这时候what引导的是宾语从句）
   

Answer 2

1. 将which改为that。因为先行词是最高级的形式，定语从句只能用that

2. 将which改为when。因为从句中不缺任何成分，when作状语，相当于on  which

3. 将what改为that 。因为从that到句末引导的是all的定语从句，当然这里的that也可以去掉，即

   This  is  all  I  know  about  the  mater.

   望采纳，谢谢！