Question To affect a vehicle, ABS: Answers Must be on all axles. Must be on the rear axle. Can be on as few as one axle. Explanation Anti-lock brakes on only a single axle still provides a driver with more control while braking than they would have without any anti-lock brakes. Take a FREE Practice Test Now This questions appears in the following tests: Kentucky Knowledge Test Class A , Arizona Knowledge Test Class B , Missouri Knowledge Test Class B , Vermont Knowledge Test Class B , New Mexico Air Brakes ,