What action should a referee take when a player commits a serious foul?

When a player commits a serious foul, the appropriate action for a referee to take is to show a red card. This action indicates that the foul was severe enough to warrant ejection from the match. Serious fouls typically involve violent conduct, such as reckless tackles or actions that endanger the safety of an opponent. Showing a red card is a clear way to maintain the safety of the players and uphold the integrity of the game.

In contrast, issuing a warning or a yellow card does not adequately address the nature of a serious foul, as these actions are more appropriate for lesser offenses. Dismissing the player immediately is also not the correct approach because a red card specifically addresses serious fouls in a formalized way, as it ensures the referee has followed the proper protocol for such offenses. Therefore, a red card is essential in deterring dangerous play and enforcing the rules of the game effectively.