If B1 is injured sliding safely into second base, who can serve as a courtesy runner?

In the context of baseball rules, when a player is injured and cannot continue playing, the role of a courtesy runner is to allow for a replacement that does not disrupt the game. The correct option indicates that the most recent batter who is not on base can serve as the courtesy runner for the injured player.

This choice is grounded in the principle of maintaining the flow of the game while providing a fair playing opportunity. By allowing the most recent batter who is not currently on base to be the courtesy runner, it ensures that the integrity and fairness of the game are upheld, as this player has just been involved in the gameplay and aligns with the order of players who are actively participating in the game.

The other options, while they may involve players associated with the team, do not adhere to the established rules regarding which players can be used as courtesy runners. For instance, using the next player in the batting order could disrupt the sequence of batters, while allowing the head coach or another player from the bench does not conform to the guidelines specific to courtesy runners, which are meant to utilize players actively engaged in the game.