How many bases must a player touch to score a run?

To score a run in baseball, a player must legally touch all four bases: first base, second base, third base, and finally home plate. This process ensures that the player has completed a full circuit of the bases, which is fundamental to the rules of the game. When a player crosses home plate after legally touching each preceding base, they are credited with a run.

The other options do not accurately reflect the requirements for scoring a run. Touching only two bases or three bases does not complete the process, and simply reaching home plate without touching the other bases would not count. Therefore, all four bases must be touched in order to legally score.