III.

1. If we plant more trees, the air won't be so polluted.

2. You can play games in the afternoon but you must do your homework in the evening.

3. In the future robots will be able to do completed things.

4. Could Ba use the computer when he was 4?

5. If we use this kind of bags, we will help the environment

6. The weather is not good. It might rains this afternoon.

IV.

1. I haven't met her before.

2. I am the thinnest person in my family.

3. How high is the tree?

4. Because of his laziness, he always gets bad marks.

5. If people throw trash into the river, the water will be polluted.

6. How long have you been collecting stamps?

7. Although I liked going out but I had to do the homeworks.