1. Sydney is the largest city in Australia.

2. I saw a very interesting film yesterday.

3. By the time I started primary school, I had learned how to ride a bicycle.

4. We've decided to stay in Hanoi for ten days.

5. What about giving a presentation about water and air pollution ?

II.

1. A lot of trees are going to be planted in the park.

2. If I had enough money, I could buy this car.

3. Because his room is untidy, his mother isn't happy.

4. I prefer listening to music to watching TV.

5. English has been learn for four years.

III.

1. English is spoken all over the world.

2 Nhi enjoyed chatting on the phone with her friends.

3. Noise pollution in big cities lead to hearing problems.

4. If you are a president in your country, what will you do to protect the environment ?

5. A lof of energy sources can be saved by recycling.