1) 定语从句 (限定性和非限定性)
There are many reasons why I want to study in your university.
It is estimated that tens of billions of yuan is spent on cigarettes every year in our country, which is a huge waste.
2) 状语从句 (时间，原因，地点，条件，让步等)
When the man is enjoying the cigarette, the smoke becomes a monster (怪物) which will devour him.
Whatever the reason, there are still some problems with student use of computers.
Mr. Kang came to our university, giving us a lecture on how to prepare for the CET Band-4.
It was him who gave up much hope for the future.
Only through these measures can we hope to solve the problem.
If so, we have to give it up.
Whatever the reason...
We totally agree with what you have just said.
Do you still remember the boy who cried wolf for several times so no one would trust him?