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CDL Practice Test
General Knowledge
Air Brakes
Combination Vehicles
Doubles and Triples
Tanker Vehicles
Hazardous Materials
Transporting Passengers
CDL Combination Vehicles Practice Test
Question 1 of 3
After pushing in the trailer supply valve you should not move the tractor until:
A
The entire air system is above 120 psi and the warning buzzer has stopped
B
The entire air system is above 60 psi and the warning buzzer has stopped
C
The entire air system is above 120 psi
D
The warning buzzer has stopped
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