Answer:

IV. 

1. It is not far from here to the nearest bus stop.You can walk to there to catch a bus.

2. You can go to opposite side the street by walking at the zebra crossing

3. When I was a child, I used to swim in the pond near my home.

4. I used to play marbles all the time when I was nine.

5. It is about 500 meters from here to my house.

6. I don't think that we can ride bicycle here because there is a road sign of not cycling.

7. It is illegal to drive on the left in Vietnam.

8. You are not allowed to ride motorbike without wearing a helmet.

9. You must obey the traffic rules for your safety and other road users.

10. I go to school on foot to keep fit and healthy.

V. 

1. My family / used / go / holiday/ seaside/ summer/.

My family used to go on holiday at the seaside in the summer.

2. He / used/ go/ school/ foot

He used to go to school on foot.

3. Now/ there/ more traffic accidents/ there / used / be / 20 years ago/.

Now there are more traffic accidents than there used to be 20 years ago. 

4. Your father/ use/ go/bus/ to work/?

Does your father go to work by bus?

5. Traffic jam / one/ most common/ issue / big city/ world.

Traffic jam is one of th most common issue in the big cities in the world

VI.

1. "I didn't often go to the supermarket every Sunday last year.

I didn't use to go to the supermarket every Sunday last year.

2. Her hair now is much longer than that in the past.

In the past her hair used to be much shorter than that now.

3. There were some flowers in the field, but now there aren't any.

There used to be some flowers in the field.

4. Don't drive too fast or you'll have an accident.

If you drive too fast, you'll have an accident.

5. Reading scientific books is one of my interests.

I'm interested in reading scientific books

6. How long is it since they bought the house?

When did they buy the house?