How much space should be allowed between the upper and lower fifth wheel after coupling?

Answer: C — No space

When coupling a combination vehicle, it's essential that there is no space between the upper and lower fifth wheel. This is crucial for ensuring a secure connection between the truck and trailer. A secure coupling prevents potential separation during travel, which can lead to accidents and loss of control over the vehicle. If there is any space present, it may indicate improper alignment or a faulty coupling, which can compromise the safety of the vehicle and the load it carries. Maintaining a tight fit ensures that the fifth wheel is engaged correctly and operates as intended during transit. Proper coupling practices are vital for the stability and safety of combination vehicles.