The correct answer is A. T-609.
A shunting order number is a unique identifier assigned to a shunting operation. It is used to track the progress of the shunting operation and to ensure that all necessary steps are taken. The shunting order number is typically assigned by the shunting supervisor and is recorded in the shunting log.
Shunting is the process of moving railway wagons around a railway yard or siding. It is used to assemble trains, to load and unload wagons, and to move wagons to and from storage. Shunting is typically carried out by a shunter, who uses a shunting locomotive to move the wagons.
The shunting order number is an important part of the shunting process. It helps to ensure that the shunting operation is carried out safely and efficiently. It also helps to track the progress of the shunting operation and to ensure that all necessary steps are taken.
The other options are incorrect because they are not shunting order numbers.