I,
1. You ought to study harder this semester
2. I haven't seen him since 1985
3. How long have you learnt E?
4. I haven't played soccer since 1995
5. I will go to HCM city in order to meet my friends
6. They used to live in Paris when they were young

7. We have lived here for 15 years
8. He has studied E for three years
9. Would you mind if I used your bike?
10. It's verydangerous to go swimming in the river 
11. Do you mind getting me a bandage?
12. Do you mind if I turn on the television?

II

1. took---> take
2. miss---> catch
3. buyed--->bougth
4. north---> nothern
5. think--->thinking
6. did---->do

I,
1. You ought to study harder this semester
2. I haven't seen him since 1985
3. How long have you learnt E?
4. I haven't played soccer since 1995
5. I will go to HCM city in order to meet my friends
6. They used to live in Paris when they were young
7. We have lived here for 15 years
8. He has studied E for three years
9. Would you mind if I used your bike?
10. It's verydangerous to go swimming in the river 
11. Do you mind getting me a bandage?
12. Do you mind if I turn on the television?
II
1. took-> take
2. so as to -> so as not to
3. buyed -> bought
4. take-> took 
5. wanted -> want
6. did -> do

I,
1. You ought to study harder this semester
2. I haven't seen him since 1985
3. How long have you learnt E?
4. I haven't played soccer since 1995
5. I will go to HCM city in order to meet my friends
6. They used to live in Paris when they were young
7. We have lived here for 15 years
8. He has studied E for three years
9. Would you mind if I used your bike?
10. It's verydangerous to go swimming in the river 
11. Do you mind getting me a bandage?
12. Do you mind if I turn on the television?