Under what condition is it considered a balk by the pitcher?

The correct answer identifies a specific action by the pitcher that clearly constitutes a balk according to baseball rules. When the non-pivot foot passes behind the pitcher's plate in an attempt to make a pick-off throw, it signifies that the pitcher has committed a violation. This is outlined in the rules that govern pitching and how a pitcher is allowed to engage with base runners.

In this scenario, the act of stepping off the rubber must be executed correctly to avoid being called for a balk. If the non-pivot foot goes behind the rubber without disengaging properly from it, it becomes illegal, leading to the balk call. The rationale here is to ensure fairness and maintain the integrity of the game, providing a clear guideline for how pitchers should legally engage in pick-off attempts.

Understanding this specific violation is crucial for umpires, as it helps maintain proper game flow and ensures that pitchers adhere to the established rules. The other conditions outlined don’t strictly meet the criteria for it to be labeled as a balk under these rules.