How does the vapour locking in a brake system occur?

How does the vapour locking in a brake system occur?

Option:

a. keeping the vehicle without use for a long period
b. over-cooling of the brake fluid in application of brake
c. overheating of the brake fluid due to frequent braking
d. taking sharp turns without applying brakes

Correct Answer : c. overheating of the brake fluid due to frequent braking

Explanation:

In automobile braking system, brake fluid is used to transmit the braking power to the brakes at wheels. The brake fluid gets heated due to application of brake. If the brakes are applied frequently then the temperature of the brake fluid raises
If the temperature of the brake fluid raises above boiling point, it becomes vapour and as the vapour is far more compressible than the liquid fluid, this results in getting brake pedal completely to the ground without any application of brake. This is a vapour lock in brake system. This a very dangerous problem since it causes an accident.