The answer is collective security because great Britain (Neville chamberlain -GB prime minister supported appeasement as the answer for the Czechoslovakia problem and then they allowed Hitler to take the Sudetenland Hitler promised to recognize Czechs new boundary lines but six months later he took over all of Czech the french Britain also supported the idea of appeasement when Hitler wanted to take Rhineland which he later did. Basically find examples why appeasement was bad and then say instead collective security was a better idea! Hope this helps! ;D