Meghan Agosta and Sara Nurse each scored in the second period, and defending gold medalist Canada clinched the top spot in pool play by edging the United States 2-1 in an early Olympic showdown between the dominant powers in women’s hockey. Genevieve Lacasse made 44 saves, and the Canadians also had two goals. Canada and the United States are the only countries to ever win gold at the Olympics. The Americans have not taken home gold since 1998, while Canada is looking for its fifth straight.