No overtaking or passing of a motor vehicle with more than 2 wheels

What is the meaning of the following traffic sign?

1. No overtaking or passing of a restricted vehicle only.
2. Correct answer: No overtaking or passing of a motor vehicle with more than 2 wheels.
3. No overtaking or bypassing of a public vehicle only.
4. No overtaking or passing of a non-motor vehicle with more than six wheels.