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CDL Practice Test
General Knowledge
Air Brakes
Combination Vehicles
Doubles and Triples
Tanker Vehicles
Hazardous Materials
Transporting Passengers
CDL Air Brakes Practice Test
Question 1 of 3
Modulating control valves are used to:
A
Apply the spring and air brakes together
B
Apply the air brakes gradually
C
Apply the spring brakes gradually
D
Switch between spring and air brakes
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