Ex 4:Rewrite these sentences using the present perfect tense
1. I (study) medicine for/since two years but then I stopped
 i have studied medicine for two years but then I stopped
2. John has worked in the restaurant for six months but then it closed
 for + số thời gian, since + mệnh đề 
3. I have lived here since I was a little girl
 
4. He has been in the prison now for three years
 
5. Nga has worked in a company since she left school
 
6. I haven't seen him since he left the office
 
7. We have been in Italy since 1960
 
Ex 6: Choose the word which has a different stress pattern from the others. Circle A, B, or C.
 
1. A. visual B. thermal C. pollute
2. A. medical B. electric C. botanic
3. A. chemical B. specific C. national
4. A. dramatic B. logical C. continue
5. A. dynamic B. festival C. illegal
Ex 7:  Choose the best option to complete each sentence. Circle A, B, or C.
1. Environmental pollution has ___________ to lots of health problems.
A. caused B. led ( lead to : dẫn đến ) C. made
2. ___________ industrial waste, many fish cannot survive.
A. Because B. Since C. Because of + N
3. Oil spills from cargos and ships have ___________ many animals and plants die.
A. made B. caused ( gây ra ) C. resulted
4. This film is rated 18+ because there are too many ___________ scenes.
A. funny B. violent ( bạo lực ) C. entertaining