In an emergency braking situation with ABS, if the brake pedal vibrates you should...

A)release the pedal so as not to lock the wheels.
B)keep braking hard.Correct
C)press the pedal intermittently.
When braking abruptly there is a risk that the wheels will lock up, with the consequent loss of vehicle control. To prevent this, the ABS anti-lock system exists, which is a safety system that prevents the wheels from locking up when braking hard.
In the event of emergency braking, if our vehicle has ABS, we must press the brake pedal all the way down and maintain maximum pressure, even if vibrations or noises occur.