Answer :
Final answer:
Securing the tractor in front of a trailer includes setting the brakes, hooking up the service and emergency airlines, and closing the tractor shut-off valves.
Explanation:
After a tractor is pulled the proper distance in front of a trailer, securing it involves several necessary steps, which, in essence, could be described as 'all of the above'.
Firstly, one must set the brakes on the tractor. This ensures that the tractor remains stationary and doesn't involuntarily move due to surface factors or environmental conditions such as wind or an inclined surface. Secondly, it is necessary to hook up the service and emergency airlines from the tractor to the trailer. This connection gives the driver the necessary control over the trailer's air brake system, ensuring the safe operation of the entire vehicle assembly.
Lastly, tractor shut-off valves should be closed to prevent air leakage when the vehicle is in a stationary mode. Closing these valves ensures that the brake system holds its pressure, keeping the vehicle safely secured until it moves again.
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