What should you do after locking the trailer brakes when uncoupling?

Answer: B — Back up gently

After locking the trailer brakes when uncoupling, backing up gently is the appropriate action. This maneuver helps to relieve tension between the tractor and the trailer. By applying gentle reverse pressure, you ensure that the trailer is properly disengaged from the fifth wheel of the tractor, which is essential for a safe and effective uncoupling process. This action allows any potential binding or pressure between the trailer and the tractor to be alleviated, ensuring that the hitch is free and that the trailer can be safely removed. It's an important step because attempting to uncouple without doing this could lead to misalignment or damage to the equipment. Safe handling of the vehicle combination requires that all steps are completed methodically to prevent accidents or equipment damage.