Which of the Following Battles Is Considered the Turning Point

Which of the following battles is considered the turning point in the war in Europe?

A) the victory of the British and Americans over the Germans in North Africa
B) the victory of the British over the Germans in the Battle of Britain
C) the American and British conquest of Sicily,which led to the overthrow of Italian dictator Benito Mussolini
D) the Soviet Union's defeat of the Germans at the battle of Stalingrad