After you supply air to the trailer, make sure the air lines are not crossed and the trailer brakes are working. This is done by
a) Applying and releasing the trailer brakes and listening for brake sounds
b) Turning on the parking brakes from the cab
c) Lifting the brake pedal
Answer: a) Applying and releasing the trailer brakes and listening for brake sounds
If the answers is incorrect or not given, you can answer the above question in the comment box. If the answers is incorrect or not given, you can answer the above question in the comment box.