Technician A says a metering valve is used to delay slightly the application of the front disc brakes..Technician B says a proportioning valve limits pressure to rear drum brakes to prevent lockup.Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Both statements are correct. A metering valve is indeed used to delay the application of the front disc brakes to allow the rear brakes to engage first for stability, and a proportioning valve is used to limit pressure to the rear brakes (especially in drum brake systems) to prevent them from locking up before the front brakes have applied sufficient stopping force.