What is the first step when uncoupling a trailer?
a.Lower the landing gear
b.Disconnect the air lines
c.Secure the trailer by chocking wheels or using parking brakes
d.Unlock the fifth wheel
Explanation
The first step in uncoupling is to secure the trailer to prevent it from moving. This means applying the trailer parking brakes and, if necessary, chocking the wheels. Safety must come first before disconnecting anything.