Chọn đáp án đúng và giải thích vì sao chọn đáp án We are using up the world's petroleum. We use it in our cars and to..(26)... our buildings in winter. Farmers are using petrochemicals to ...(27)... their soil rich. They use them to kill insects that eat plants. These chemicals go into the rivers and lakes and kill fish there. Thousands...(28)...pollutants also go into the air . Winds this polluted air to other countries and other continents. Poor farmers use the same land over and over. The land needs a rest so that it will be better next year...(29)the farmers must have food for this year. Poor farmers cut down forests for firewood. In some areas when the are gone, the land...(30)...a desert. Poor people can not save environment for the future. 26.A.heated B.heat C.cool D.hot 27.A.turn B.let C.make D.change 28.A.0 B.of C.this D.these 29.A.but B.though C.however D.therefore 30.A.turns B.converts C.gets D.becomes