To achieve a victory in Europe, the Allies needed to create an effective A sea and air attack.
B two-pronged attack.
C three-pronged attack.
D sea and ground attack.

Correct answer is C. three-pronged attack.

Explanation:

C is the correct answer because Allies had to attack Germany first of all from all sides. That is why Operation Overlord was put into motion. Anglo-American forces were to attack the German forces on the shores of Normandy while in the same other Allied forces, first of all Soviet will push forward from east and south. Eventually, this led to collapse of Axis Power.

Therefore, all other options are not correct as they were not sufficient.

i think it's a)sparta