Which of the following statements is true of a residual check valve?
a. a residual check valve warns the driver of a loss of pressure in one of the two separate systems by lighting the dashboard red brake warning indicator lamp.
b. a residual check valve regulates pressure to the rear brakes in proportion to the pressure applied to the front brakes.
c. a residual check valve lights the red brake warning lamp on the dash if low brake fluid level is detected.
d. a residual check valve keep the wheel cylinder sealing cups tight against the inside wall of the wheel cylinder.

option D

Explanation:

the correct answer is option D

residual check valves are used on drum brakes system to maintain the low pressure inside the brake system even after the break paddle is released.

This low maintenance of pressure will not allow air to enter in the breaking system.

So, a residual check valves helps keep  wheel cylinder sealing cups tight against the wheel cylinder to prevent air entrance.

sonar - device which is used to find the submit submarines, sankalp ship. sonar waves consists of a transmitter and detector which are installed in the observation centre on board of a ship. the ultrasonic waves are sent into the sea at high frequency about 1000 khz in all direction.