I believe the correct answer is Sobechi, who can follow the rules of a game.
Jean Piaget considered the stage of concrete operations, third stage of cognitive development, as a major turning point in the child's cognitive development. In this stage child learns think logically and understands the concept of hierarchy. Therefore, Sobechi, who can follow the rules of a game has entered the stage of concrete operation as he can now think logically and understands that there are rules and hierarchy.