The trailer spring parking brake valve is responsible for several important functions: It ________ and _________ the front service reservoir from the rear service reservoir. This is important as it prevents an automatic application of the __________ _________ _______ if one of the reservoirs were to lose _____ __________.
a. protects, isolates, trailer spring brakes, air pressure b. activates, combines, emergency brakes, hydraulic pressure
c. engages, separates, transmission brakes, brake fluid
d. regulates, connects, parking brakes, nitrogen pressure