The correct answer is A.
Operation Overlord was also known as D-Day.
During WWII (1939 - 1945 ) the battle of Normandy, which lasted from June 1944 to August 1944, resulted in the allied liberation of Western Europe from Nazi Germany's control.
Codenamed Operation Overlord, the battle began on June 4 1944, a day that was also known as D-Day, when 156,000 American, British and Canadian Forces landed on five beaches along the heavily fortified coast of France's Normandy region.