Which of the following must the second referee have?

The second referee must be equipped with a variety of essential tools to effectively perform their role during a volleyball match. This includes having a coin and a watch for managing the starting serve and ensuring that the match begins on time. The lineup card is crucial because it allows the second referee to keep track of the players on the court for substitution purposes and for checking rotations. Furthermore, the set of red and yellow cards is necessary for any disciplinary actions that may need to be taken during the match, along with a pen or pencil to note important information.

Having all these items ensures that the second referee can oversee the game in an organized manner, maintain order, and adhere to the rules effectively. The presence of each of these items supports the second referee's responsibilities in ensuring fair play and efficient management of the match. Therefore, the necessity of having all these tools makes the choice that suggests they must possess all of them the correct one.