What must a train have to leave an interlocking and enter 410 territory?

To leave an interlocking and safely enter 410 territory, a train must receive the proper signals that provide the necessary indication for proceeding. The selection of "All of the above" is correct because it encompasses all possible signals that would allow for the safe entry into that territory.

An Absolute Clear signal indicates that the track ahead is clear and that the train may proceed at its maximum speed. An Absolute Medium Clear signal indicates that while the train may proceed, caution is advised, as there may be conditions ahead that require the train to be prepared to stop or slow down. Similarly, a Flash Slow Approach signal indicates that the train must approach the next signal cautiously, as there may be something requiring attention in the path ahead.

Each of these signals serves a distinct purpose, ensuring that the train enters the territory safely under different operational conditions. Therefore, possessing any one of these signals means the train can leave the interlocking and enter 410 territory while adhering to safe operational standards. All possible signals are essential components of train operation, which is why "All of the above" is the correct answer.