As we all know, reading is very important.
Reading is very important, which we have already known when we were very young.
He failed in the exam again, as was expected.
He failed in the exam again, which was unexpected.
Jack was admitted into the university, as we had expected.
as has been said before as often happens
as is well known as we all can see
the same…as such…as
He passed the exam, which made him delighted.
They went to the zoo, after which they saw a film.
He can write a letter in English, which I cannot.
Beijing, which he was born, is our capital.
Lily thought me clever, which she herself was.
在定语从句中，相比于which VS that，who VS that，我们对which与as两者区别的关注度要少很多，在遣词造句或是口语表达中，也常常是“跟着感觉走”。