Put the verbs in brackets into the correct tense

1. We ______ (to study) the properties of this material before we began to use it.

2. Temperature changes ______ (to affect) nearly all properties of matter.

3. Pierre and Marie Curie _________ (to discover) radium in 1898.

4. Electromagnetic waves _________ (to travel) with the velocity of light.

5. Here you are at last! I _________ (to look) for you.

6. We (to start) our experiment next week if everything ___ (to go on) well.

7. Do you realize what you ________ (to say).

8. For four years this expert _______ (to work) at his subject.

9. Changes continually ____ (to take place) in the properties of bodies around us.

10. His family ______ (to stay) in the village while Nick (to take) his exams.

11. Note the direction in which the conductor _______ (to move) in the magnetic field at this moment.

12. How long you ____________ (to study) at the university?

13. By the end of the week we ______ (to spend) all our money.But by that time I hope, I _______ (to find) a job.

14. My watch stopped as I _______ (not to wind up) it.

15. You ______ (to read) anything about nuclear physics?

16. They ______ (to test) the new device this week. The test was successful.

17. When night ______ (to come) some of physicists _______ (to stop) their research in the laboratory, but the others still ____ (to continue) working over the experiments.

18. He ______ (to publish) the results of his working out that he ______ (to carry out) for many years.

19. When we _____ (to arrive) at the university, the classes _ _____ (not to begin) yet. The students _______ (to hurry) to take their places, when the professor _______ (to come in).