Final answer:
The effectiveness of anti-lock brakes increases when they are pumped because it activates the ABS system. This system momentarily decreases the brake force to prevent the vehicle wheels from locking, which consequently, maintains grip and prevents the vehicle from going out of control.
Step-by-step explanation:
The question is asking how pumping anti-lock brakes contribute to their effectiveness. The correct answer is C) It activates the ABS system. Anti-lock braking systems (ABS) work by rapidly pumping the brakes for the driver in scenarios where an unplanned, immediate stop is needed. A sensor in the system detects if a wheel is on the verge of locking up and, if it is, the ABS momentarily decreases the brake force on that wheel to prevent the skid. The system then rapidly reapplies the brakes, in effect pumping them, thus increasing the effectiveness of the brakes and enabling the vehicle to maintain grip and preventing the vehicle from skidding out of control.
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