Here are the corrections needed for the underlined parts:

1. **(A)** should be "Motorists should always wear a helmet..."
2. **(A)** should be "It is just some..."
3. **(A)** should be "How long is it from your house..."
4. **(C)** should be "is illegal in many..."
5. **(B)** should be "heavy vehicles..."
6. **(A)** should be "How far is it from Cao Bang City to..."
7. **(A)** should be "A flashing DON’T WALK signal indicates..."
8. **(B)** should be "hold an adult's hand..."
9. **(A)** should be "It usually takes him thirty minutes..."

Make sure to adjust any grammar and phrasing as necessary in the context of your sentences!