单项选择题

Chess must be one of the oldest games in the world. An Arab traveler in the year 900 wrote that it was played "long, long ago". Chess was probably invented (发明) in India, and it has been played everywhere from Japan to Europe since 1400. The name "chess" is interesting. When one player is attacking the other’s king, he says, in English, "check". When the king has been caught and cannot move anywhere, he says "checkmate". These words come from Persian words "Shah mat", which means "the king is dead". That is when the game is over, and one player has won.
Such an old game changes very slowly. The rules have not always been the same as they are now. For example, at one time the queen could only move one square at a time. Now she is the strongest piece on the board. It would be interesting to know why this has happened Chess takes time and thought, but it is a game for all kinds of people. You don’t have to be winner in order to enjoy it. It is not always played by two people sitting at the same table. The first time the Americans beat the Russians was in a match played by radio. Some chess masters are able to play many people at the same time. One man played 400 games! It is said that some people play chess by post. This must make chess the slowest game in the world. Chess ______.