Practice question

When charging a trailer during the combination-unit inspection, the trailer brakes do not release. What is the best immediate interpretation?

The supply and control lines may be crossed or the trailer is not charging correctly
This is normal and proves the trailer service brakes work
The tractor low-air warning is automatically defective
The driver should drive away to warm the drums

Answer: A — The supply and control lines may be crossed or the trailer is not charging correctly

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