What action can lead to a direct free kick?

Fouling an opponent by tripping them is a clear violation of the laws of the game and results in a direct free kick. According to the Laws of the Game, a direct free kick is awarded when a player commits a foul such as tripping, pushing, or holding an opponent. This type of foul hinders the opponent’s ability to play the ball and could potentially lead to serious injury, which is why the laws are strict in this area.

The other options listed do not lead to a direct free kick. For instance, offside positioning during play results in an indirect free kick for the opposing team, but it is not classified as a foul on an opponent. Retaining possession of the ball beyond a certain time limit is not governed by a free kick law; the game allows players to maintain control as long as they actively attempt to play the ball. Additionally, a player leaving the field without the referee's permission may result in a stoppage of play or specific actions by the referee, but it does not directly cause a free kick. Thus, tripping an opponent is the only action among the choices given that results in a direct free kick.