The unity of knowledge and action means that knowledge and action become one.

This method is very effective.

This painting is very expensive, making it difficult for ordinary people to buy.

The Prime Minister held a press conference at the official residence.

He is known as the best pupil of that teacher.

The official rate of that currency has been changed.

This voyage is long, isn't it?

We are considering a revision of the contract.

He worked all night to revise his thesis.

I was asked to revise this thesis.