The teacher is writing ____ a piece of chalk on the blackboard while the students are writing ____ink in exercise books.
Something must be done to prevent our city ____ by thick smoke.
To tell you the truth, I have nothing to do ____ it.
Did you have any trouble ____ the post office?
- How long has the bookshop been in business? -____1982.
He looked quite healthy ____ he was ____ the age of seventy.