The correct answer is A. T-806 + Caution order.
T-806 is an authority to run a train in the wrong direction. It is issued by the train dispatcher and is valid for a single trip. The caution order is a document that is issued by the train dispatcher to the train crew. It provides information about the temporary single line working and the precautions that must be taken.
T/D 602 is an authority to run a train on a single line. It is issued by the train dispatcher and is valid for a single trip. T-511 is an authority to run a train on a double line. It is issued by the train dispatcher and is valid for a single trip.
T-1425 is an authority to run a train on a single line with a speed restriction. It is issued by the train dispatcher and is valid for a single trip.
In the case of temporary single line working on a double line section on Absolute Block system, the train dispatcher will issue an authority to run the train in the wrong direction (T-806). The train crew will also be issued a caution order (which provides information about the temporary single line working and the precautions that must be taken).