Which among the following date in world history is know

Which among the following date in world history is known as D-day, a date also known as of Operation Neptune and Operation Overlord ?

[A] 3 March 1943
[B] 6 March 1943
[C] 6 June 1944
[D] 6 June 1945

This question is part of UPSC Prelims Practice and Mock Tests membership programme.