Such problems （ ） air pollution and traffic jams are becoming more and more serious in some big cities.

It was in the factory （ ） you worked five years ago （ ） you learned the technique.

I can’t attend Mary’s birthday party next Sunday evening. （ ）, I thanked her for her kindly invitation.

When we arrived at the airport, we were told our flight （ ）.

Air pollution is obviously one of the major _____ of city life.

Only when （ ） in the afternoon （ ） able to leave.

_____ breaks the law will be punished sooner or later.

“（ ） everyone’s here,” she said, “let’s begin to discuss the solution to the problems we have found．”

It is （ ） impossible to work with this noise around.

The doctor said that mental （ ） is the major cause of his sleeping problem.

The quality of education in this small school is better than _____ in some larger schools.

From her conversation, I_____that she had a large family.