During a dead ball, what can the playing captain request regarding their opponent?

In volleyball, during a dead ball situation, the playing captain can make specific requests regarding their opponent to ensure the game is being played fairly and within the rules. One such request involves the verification of the proper server. This is crucial as the server must be in accordance with the team's rotation and should not be out of order. The team captain has the right to question if the server is legal and if they are indeed recognized as the designated player to serve at that moment. This helps maintain the integrity of the game and ensures adherence to the established order of play.

The captain's ability to verify the proper server directly ties into the rules surrounding serving and rotation, which are fundamental for fair play. The other options mentioned do not apply in the same way during a dead ball. For instance, verifying the libero or team serve order may be done under different circumstances or by other officials, but the immediate concern during a dead ball is specifically about the server and the legality of their action.