Answer: B. Grand Coulee Dam is the largest in the United States.<em> The dam is higher</em> than twice of <em>the Niagara Falls.</em> The Grand Cooley Dam on the Columbia River (Washington) was built to control floods, irrigate irrigation, provide hydroelectric energy and regulate the level of the river. <em>The dam consists of concrete</em> and at the expense of its weight withstands the pressure of water mass, ice. There are exist<em> 14 dams on the Columbia River</em> (3 in Canada and 11 in the United States).