sentence: A group of people play polo on horses on  a grass covered, fenced in field surrounded by onlookers and spectators. sentence:    A man on a horse walks down the center of a line of people on a horse while holding a long mallet pole. sentence:   A group of spectators standing and sitting on the grass look on from the side of the field. sentence:   The game of polo begins and the people on the horses begin to swing their mallet poles across the ground.