In what situation is dropping the ball considered a balk?

The scenario in which dropping the ball is considered a balk is when the pitcher is in the set position and the ball does not cross the foul line. In this situation, the pitcher is required to maintain control of the ball. Falling to the ground or letting the ball drop is an indication of losing control, which constitutes a violation of the rules regarding pitching actions. The rules are designed to ensure that the pitcher maintains their focus and doesn't mislead the runners or the batter.

The context of this situation is critical; it underscores the importance of pitcher actions when in the set position. A pitcher's failure to properly manage the ball while in that position can disrupt the flow of the game and create unfair advantages or confuse the baserunners.

The other options reflect scenarios that do not lead to a balk. For instance, if there are no runners on base after the windup, the pitcher has more leeway and dropping the ball does not incur the same penalty, as there's no one to deceive. The same applies during the delivery when the batter is ready, as this is a more regulated phase of play where dropping the ball doesn't affect any players. Stepping backward off the plate relates to the pitcher's mechanics but doesn't result in a balk under those specific circumstances