CDL combination vehicles practice

You drop an older trailer built before 1975 at a customer lot. It has emergency brakes that work from its own air tank but no spring brakes. What does the CDL manual tell you to do?

• APull the air supply knob; the emergency brakes will hold it.
• BLeave the air lines connected to a dummy coupler to hold air.
• CChock the wheels, because the stored air will leak away.
• DSet the trailer hand valve before you disconnect the lines.