The Warsaw pact was the Soviet response to the Western alliance known as Nato. So the correct option for the given question is option "B". In the year 1949 United States of America and its eleven Western allies came together to form North Atlantic Treaty Organisation. This organisation was formed in fear of more communist expansion by Soviet Union. To challenge NATO, Soviet Union came up with a pact including the communist nations of Eastern Europe, which came to be known as the Warsaw Pact.