Khí SO₂ (sinh ra từ việc đốt các nhiên liệu hóa thạch, quặng sunfua) là một trong những chất gây ô nhiễm môi trường, do SO₂ trong không khí sinh ra: 

BT câu tường thuật pha trộn negative và positive

1, I often have a big hamburger => Benjamin says

2, If I were you, I’d stop talking tranquilizers. They won’t be good for you health in the long run => I said

3, Frank: How much pocket money Does Lisa get?

4, Don’t touch that wire, will you => Said the mother

5, Patricia: My mother will celebrate her birthday next weekend

6, I’m sorry I’m late => He said

7, Shall I do the cleaning up for you? => He said

8, If I were you, I would buy that book => she said

9, Why don’t we go to the cinema tonight? => He said

10, Would you like to come to my birthday party next Saturday? => She said