You didn't use to like him much when we were at school, __________?
Scientists are convinced the positive effect of laughter physical and mental health.
Playing basketball is great fun; it also provides us with a chance to develop our sense of team spirit.
It is hard to say what kind of person he is. Sometimes he is very friendly; at other times he ___ be very cold.
In my opinion, ___ matters is not one’s looks, but one’s inner thoughts.
_____ computers are convenient to us in daily life, it may also cause other problems.