Put the Verbs in the brackets in the correct forms

1. For many years scientists (to study) the nucleus before they found that it is possible to split it.

2. Many power stations (to use) atomic energy for a long time before I knew it.

3. All this period scientists and engineers (to develop) rocket technology and electronics in close cooperation.

4. We widely (to use) electronic devices in industry for many years.

5. We know that our astronomers (to observe) the moon for a long time.

6. My friend (to make) these experiments to compare the weight of elements since the first of September

7. The question about the new experiment on this subject (to discuss) for some time before we came to a definite conclusion.

8. The fact that atom has a nucleus in its center, which is positively charged, (to discuss) by Ernest Rutherford in 1911.

9. This problem (to solve) in the near future.

10. The phenomenon of radioactivity (to use) widely in industry, medicine and agriculture

11. He found that this effect (to cause) by some unknown subatomic particles.

12. The weights of these particles (to calculate) with the help of electronic computer.

13. U-238 (to convert) into plutonium and then (to use) to generate atomic power.

14. These substances (to refer to) usually as hydrogen isotopes

15. One of the isotopes of hydrogen (to call) deuterium.

16. He (to puzzle) by these unexpected results.

17. It (to show) that these substances differed greatly in their chemical properties.

18. It (to expect) that the results of our research (to apply) in chemical industry.