It is common knowledge that honesty is the best policy.
It is well-known that...
It is self-evident/ conceivable / obvious / apparent that...
It goes without saying that... It is universally acknowledged that...
It is / that
We cannot underst and why he was so cruel to his roommates.
The problem is not who will go, but who will stay.
As is shown/ demonstrated/ illustrated/ depicted/ described...in the cartoon/ picture/ graph/ table...,
There are many reasons why I want to study in your university.
It is estimated that tens of billions of pounds spent on cigarettes every year in our country, which is a huge waste.
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.
Prof. Kang came to our university, giving us a lecture on how to acquire English better.
Only through these measures can we hope to solve the problem.
Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots.
Some measures should be taken to deal with the problem.
He is said to have accomplished a lot of great deeds.
Many people believe that...（It is believed that...）
Do you still remember the boy who cried wolf for several times so no one would trust him?