Which of these is a foul in volleyball?

Volleyball is a popular team sport in which two teams of six players are separated by a net. Each team tries to score points by grounding a ball on the other team's court under organized rules. It has been a part of the official program of the Summer Olympic Games since Tokyo 1964.

Common faults include: contacting the net, lifting the ball, blocking a serve, hitting the ball two times in a row, stepping over the service line on a serve, reaching over the net (unless during a block or follow-through of a spike), or reaching under the net. Additionally, it is a fault when a back-row player spikes or blocks the ball in front of the attack line. Serious violations result in a yellow card (warning) or red card (ejection from the game).

Other officials include line judges, who assist the referee by calling the ball out of bounds at the end lines, which is signaled by the use of hand gestures or flags.