What condition must be met for a player to remain a snapper during a play?

The condition that allows a player to remain a snapper during a play is that they must have a reasonable opportunity to regain balance and protect themselves. This rule is put in place to ensure the safety of players, particularly the snapper, who is often in a vulnerable position just before the snap.

When a snapper is engaged and then moves as the play begins, they might find themselves in a position where they could be at risk of injury, particularly from defenders who are trying to rush the quarterback. Allowing the snapper time to regain their balance and protect themselves helps mitigate such risks.

In contrast, the other choices do not align with the fundamental requirement for a player to maintain their role as a snapper. For example, blocking an opponent before the snap is not a condition; the snapper’s primary role is to snap the ball rather than engage in blocking beforehand. Moving to participate immediately would imply that they are no longer in the snapper position, and remaining stationary until the whistle blows doesn't account for the dynamic nature of the play that allows for some movement after, as long as the snapper can still regain their balance.