When can a pitcher throw or feint to a base?

A pitcher can throw or feint to a base when their pivot foot is clearly behind the pitcher's plate. This rule is in place to ensure that the pitcher is not gaining an unfair advantage before attempting a pick-off or throw to a base. The position of the pivot foot behind the pitcher's plate allows the pitcher to legally make a play on the base without violating the rules governing balks or illegal pitches.

In situations where the pitcher does not have his pivot foot behind the pitcher's plate, any attempt to throw or feint could be deemed illegal, resulting in a balk. This stipulation maintains fairness in the game, as it allows the base runners to advance without being unfairly penalized.

The other options do not align with the regulations governing the pitcher's actions. For instance, raising both feet or being in the stretch position does not inherently grant the pitcher the right to throw or feint to a base, and while having a runner on base may increase the necessity for such actions, it does not dictate when a pitcher can perform them under the rules.