What defines a potential screen in volleyball?

A potential screen in volleyball occurs when the position or behavior of players impacts the ability of the opposing team to see the ball clearly during critical moments, particularly during a serve. The correct answer encompasses all scenarios that could obstruct visibility.

When players stand too closely together or directly in the line of sight of the server, it can create a barrier that makes it difficult for the receiving team to track the ball. This is particularly pertinent in volleyball during service because the serve initiates play and the receiving team's ability to respond effectively can be hindered by any obstacles in their line of sight.

Waving arms while serving can also contribute to a screen effect, as it distracts the opponents or further obstructs their visual field. Group formations that are tightly clustered can exacerbate the problem, especially if they are positioned strategically to block the view of the serve.

Thus, all the presented scenarios collectively describe forms of potential screens that could be called for penalty if deemed to disrupt fair play by impairing the visibility of the incoming serve for the receiving team.