I. Complete each sentence with one suitable preposition. 1. The new policy has led…………….. three major strikes in the city today. A. to B. in C. for D. at 2. The poisonous chemical waste is dumped……………..the river. A. to B. into C. for D. at 3. Scientists have come up…..new ways of saving money. A. with B. in C. for D. at 4. The oil spill resulted …….the death of thousands of fish in this sea. A. to B. in C. for D. at II. Complete the sentences with the types of pollution. 5.  …………….. occurs when the atmosphere contains gases, dust, or fumes in harmful amounts. 6. When radiation goes into the land, air or water, it is called…………….. 7. Too much use of electric lights in cities may cause…………….. 8. …………….. happens when human activities destroy the Earth's surface. 9. …………….. is the contamination of lakes, rivers, oceans, or groundwater, usually by human activities. 10. …………….. occurs because there are too many loud sounds in the environment. 11. The sight of too many telephone poles, advertising billboards, overhead power lines, or shop signs may cause…………….. 12. When…………….. happens, the water temperature in streams, rivers, lakes, or oceans changes. III. Put the verbs in brackets into the correct form. 13. Our garden is so beautiful. There (not be) …………….. any flowers if my sister (not take care) ……………….. of it every day. 14. If I (be) …………….. you, I (wear) …………….. earplugs when going to the concert. IV. Rewrite these sentences beginning with the words given, using if-clauses. 15. Dick can’t find the way because he doesn’t have a map.  If 16. I can’t send her the letter because I don’t know her email address.  If 17. He is not a doctor, so he can’t help me.  If 18. She can’t send her children to school because she is poor.  If 19. Nam doesn’t study hard. Therefore, he fails the exam.  If