ASVAB Practice Test

The master cylinder is responsible for applying hydraulic pressure to the wheel cylinders, which in turn cause the brake shoes or pads to press against the brake drums or rotors. This creates friction and slows down the vehicle. Options A, C, and D are incorrect because they refer to functions that are not related to the master cylinder. Option A mentions brake calipers, which are part of the braking system but are not directly affected by the master cylinder. Option C refers to engine oil pressure, which is unrelated to the braking system. Option D mentions coolant temperature, which has no impact on braking. Therefore, B is the most accurate and logical answer for the function of the master cylinder.