---Which of the three optional courses did you like best, Joe? ---To tell you the truth, I didn’t like _______ of them.
---How long has the United Nations ________? --- ______1945.
Dr. Black is a professor of chemistry. _______, he is a famous writer.
The new invention may __________a lot of changes in our daily life.
It _______ them three years to build this road.
I wanted _______ you for your last letter.