Read this and answer the question. If the question is unanswerable, say "unanswerable".

The referee may punish a player's or substitute's misconduct by a caution (yellow card) or dismissal (red card). A second yellow card at the same game leads to a red card, and therefore to a dismissal. A player given a yellow card is said to have been "booked", the referee writing the player's name in his official notebook. If a player has been dismissed, no substitute can be brought on in their place. Misconduct may occur at any time, and while the offences that constitute misconduct are listed, the definitions are broad. In particular, the offence of "unsporting behaviour" may be used to deal with most events that violate the spirit of the game, even if they are not listed as specific offences. A referee can show a yellow or red card to a player, substitute or substituted player. Non-players such as managers and support staff cannot be shown the yellow or red card, but may be expelled from the technical area if they fail to conduct themselves in a responsible manner.

Which card does a referee avoid to signal a caution to a player?
unanswerable