1. If I (to see) John, I (to tell) him your news. 2. He (to be) very pleased if it (to be) really true. 3. If you (to go) to town on Monday, you (to meet) my brother Tom. 4. If you (to need) help, my father to help you. 5. We (to have) a picnic lunch if the day (to be) fine. 6. If you (to ask) a policeman, he (to tell) you the way. 7. I (to finish) the job tomorrow if I (to can). 8. I (not/to require) an umbrella if it( not /to rain). 9. If she (to think) it over carefully, she (to form) a clear opinion. 10. If they (to catch the bus now, they (to arrive) at half past nine. 11. He (to find) the answers if he (to look) at the back of the book. 12. If you ( to want) me to, I (to come) for a walk with you. 13. If he (to write) to her, she (to answer) at once. 14. If you ( to wait) a few moments, the waiter (to bring) your coffee. 15. He (to lose) weight if he (to stop) eating too much. 16. If she ( to be) patient, I (to try) to explain. 17. I to wear) a purple tie only if I (to must). 18. If we (to leave) at once, we (to catch the early train. 19. If he (to do) that again, his father (to punish) him. 20. If she (drink) this medicine, she (to feel) much better. 21. If Alice (not feel) well tomorrow, she (to stay) at home with her little brother and sister. 22. The alarm (to ring) if Peter (not wake) up in time.
Acid rain is caused (Present Simple Passive) by burning coal and oil. When either fuel is burned (Present Simple Passive), it releases poisonous gases which are carried up (Present Simple Passive) into the atmosphere and sometimes transported (Present Simple Passive) long distances.
Over 3,000 research projects have been carried out (Present Perfect Passive) to look into acid rain, and a decision to solve the problem has been taken (Present Perfect Passive) in most of the western European countries. Measures have been taken (Present Perfect Passive) in Scandinavia and in Central Europe to stop the pollution before it has destroyed the environment, and a diplomatic campaign has been launched (Present Perfect Passive) to convince other countries that the problem has to be considered as a major ecological threat.
“Five years ago this issue was not being treated (Past Continuous Passive) seriously,” says one leading environmental group, “but now that damage has been reported (Present Perfect Passive) in large areas of forest and Lakeland, our politicians are being forced (Present Continuous Passive) to take action. This problem must be solved (используется модальный глагол must) quickly: if governments do nothing, they will be faced (Future Simple Passive) in two or three years’ time with accusation that they have allowed our forests to die.”