What is a player allowed to do immediately after being sent off?

A player who has been sent off is indeed typically required to leave the field immediately and cannot remain on the pitch to observe the game. In general practice, players are expected to leave the vicinity of the field to maintain the integrity and discipline of the game.

However, staying in the team locker room with a chaperone is a permissible option. This allows the player to remain part of the team's environment while ensuring that they do not have any unsupervised interactions with other players or officials that could lead to further disciplinary issues. The presence of a chaperone is crucial as it helps to monitor the conduct of the sent-off player, making sure that they do not engage in any activities that could disrupt the match or violate disciplinary protocols.

The other options do not align with standard disciplinary measures. For instance, attending the post-match press conference could lead to inappropriate comments and further escalate tensions, and leaving the stadium immediately could prevent the player from being available for any necessary discussions with team officials regarding the incident. Therefore, staying in the team locker room with supervision is the most appropriate course of action following a red card.