Answers:
Canada, United States, and Britain.
Step-by-step explanation:
D-day operation in Normandy refers to the day of the invasion of Normandy (June 6, 1944) by the Allied Forces in the context of WWII. This invasion allowed the Allied forces to establish a front of attack from Western Europe that would ultimately mark the beginning of the fall of Germany during WWII. The three countries mentioned in the answer were the main forces behind the land attack, along with the Free French Forces. Other nations in Europe also participated in this war effort.