The statement that best evaluates President Franklin Roosevelt's strategies for persuading more Americans to abandon isolationist policies after the beginning of World War II in Europe is:
C. Roosevelt convinced Americans that U.S. involvement in the war was necessary after the surprise attack on Pearl Harbor by Japanese forces.
This statement is accurate because the attack on Pearl Harbor on December 7, 1941, was a pivotal moment that shifted public opinion in favor of entering the war. Prior to this event, many Americans supported isolationist policies, but the attack galvanized the nation and led to widespread support for joining the conflict.