sentences:  Due to the nature of the sport, quick retrieval of loose balls and delivery of the game balls to the servers are necessary for quick play in tennis.In professional tournaments, every court will have a trained squad of ball boys/girls with positionings and movements designed for maximum efficiency, while also not interfering with active play.As well as dealing with the game balls, ball boys/girls may also provide the players with other assistance, such as the delivery of towels and drinks.