What can the libero do when positioned behind the attack line?

When the libero is positioned behind the attack line, they are allowed to set the ball using overhead finger action. This is significant because the libero traditionally plays a defensive role and has specific restrictions regarding attacking the ball. When the libero is in a back-row position, they can make a play on the ball, including setting it, which involves using overhead finger action. This action can aid the team in transitioning from defense to offense by delivering a well-placed ball for attackers.

In contrast, the other options detail actions that are generally restricted or prohibited for the libero. For example, blocking is a role that is reserved for regular players, and liberos are unable to participate in blocking an opponent's attack. Additionally, attacking the ball over the net from anywhere, including the front or back row, is not permitted unless the libero is behind the attack line and playing the ball in a specific manner. Finally, setting the ball from any position disregards the technical rules governing the libero's function and responsibilities on the court. Only when behind the attack line can the libero attempt certain plays while adhering to the rules.