What is the main function of the auxiliary brake (hand/parking brake)?

1. To assist new drivers in downhill braking.
2. Correct answer: To make sure that the vehicle doesn’t move while parked.
3. The auxiliary brake (hand/parking brake) has no function and it shouldn’t be used at all.
4. To enhance the braking capacity of the service/leg brake.

WhyThe handbrake keeps the vehicle from rolling away while parked.