C. The massive amount of Allied forces landing in Normandy caused the German army to retreat and the Allies to reclaim France.
Explanation:
The Normandy Landings, also known as the D-Day, were the first meaningful counterattack from the Allies to Germany. It was a massive attack in Northern France which was already captured by Germany and allowed Allies to move forward into French territory regaining control of different communes such as Bayeux, Caen and Caretan just in one day. The D-Day was the beginning fo German retreat from France.
