Swimming - Ledecky makes Rio debut in relay

By Alan Baldwin RIO DE JANEIRO (Reuters) - Freestyle phenomenon Katie Ledecky made an impressive Rio debut with the fastest leg for the U.S. women in their 4x100 relay heat on Saturday. The 19-year-old, who could win three individual freestyle events at the Games to add to her 2012 800m freestyle gold, had been uncertain for the team but her time showed why she had been selected. World and Olympic champions Australia, with sisters Cate and Bronte Campbell powering the charge, were fastest with t