Q
76. Describe what the service line is for?
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Aa. To carry air to the parking brake to control the trailer brakes.
Bb. To carry air to a relay valve that allows the trailer brakes to be applied quickly.
Cc. To carry air to the cab of the rig to cool it.
Detailed Explanation
The correct answer is "b. To carry air to a relay valve that allows the trailer brakes to be applied quickly.". This is based on federal CDL regulations and safety standards.
Correct Answer: b. To carry air to a relay valve that allows the trailer brakes to be applied quickly.
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