Употребите модальные глаголы could,should,ought to там,где необходимо.
1) When I was young, I ...run very fast.
2) Paula ...not go to the meeteng last week. She was ill.
3) When you play tennis, you ...watch the ball.
4) If you have time, you ..go to the Science Museum. It's very interesting.
5) We ...not wait very long for the bus yesterday. We didn't have much time.
6) It is very important that everybody ...listen very carefully.