We had no sooner sat down to eat( )the phone rang.(than/when) 英语讲讲原因,谢谢

题目

We had no sooner sat down to eat( )the phone rang.(than/when) 英语讲讲原因,谢谢
The dentist had hardly turned round( )the patient realized he had taken out the wrong tooth.(than/when)为什么这两句一个用than,一个用when.讲讲than的用法谢谢

答案

no sooner...than...
hardly ...when...
这两个表示一.就.的句型是固定的搭配.