What step follows disconnecting the air lines and light cable during uncoupling procedures?

Answer: A — Pull secondary and primary pins

After disconnecting the air lines and light cable during uncoupling procedures, the next step is to pull the secondary and primary pins. This action is essential as it allows for the trailer to be released from the tractor safely. The primary and secondary locks are mechanisms that secure the trailer to the tractor, and disengaging them is critical to ensure that the trailer can be safely separated without causing any damage or hazards. This step is part of the fundamental safety protocols involved in handling trailer connections, ensuring that the operation is smooth and adheres to the required procedures. Properly following this step helps to prevent accidents that could occur from improper separation of the vehicle components, as it ensures that everything has been disengaged before the trailer is detached.