请教老师下面句子中的（）里可以填which吗?还是填as呢,还是都可以啊

题目

请教老师下面句子中的（）里可以填which吗?还是填as呢,还是都可以啊
The British are not so familiar with different cultures and other ways of doing things,( ) is often the case in other countries

答案

只能填as引导定语从句,这是固定结构. 即as is often the case
类似的还有：
as is mentioned above
as is often said
as is well known to all
as often happens等