Serena Williams of the United States returns the ball during the ladies' singles final against her sister Venus Williams at the 2009 Wimbledon Tennis Championships at the Centre Court in Wimbledon of London July 4, 2009. [Xinhua]

Serena Williams of the United States reacts during the ladies' singles final against her sister Venus Williams at the 2009 Wimbledon Tennis Championships at the Centre Court in Wimbledon of London July 4, 2009. [Xinhua]