Q
99. Charge the trailer air brake system and push the air supply knob in. Shut the engine off. Step on and off the brake pedal several times to reduce the air pressure in the tanks. The trailer air supply control should pop out when the air pressure falls
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Aa. This is how you test the tractor protection valve.
Bb. This is how you test the trailer's suspension.
Cc. This is how you test the tractor's horn.
Detailed Explanation
The correct answer is "a. This is how you test the tractor protection valve.". This is based on federal CDL regulations and safety standards.
Correct Answer: a. This is how you test the tractor protection valve.
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