It's very important to have a teacher… .............. knows his subject.

My friend was sick, so I had to go to the party………….

Mr. Smith just ...... his new book last week. He hopes it will be successful.

The teacher told students .................. about the exam.

The boys' mother told them to finish all of their breakfast , ...... they stuffed their mouths until their plates we…

If you had taken better care to do your research, a lot of time could……..