he gained the support of the working class
The question is kind of tricky. D-Day was the code word for the Allied invasion of France, so D is definitely a possible answer. But the PURPOSE of that invasion was in part to defend Britain, which at the time was being threatened by Nazi air attacks and by a possible Nazi invasion. So A is possible as well.
The overthrow of Mussolini was certainly a factor in the Allied strategy, but the invasion of Italy, not France, was how that task was accomplished. So C is out.
There's competing evidence over how much the Allies knew about Auschwitz by the time of D-Day. Either way, the immediate purpose of D-Day was not to free the Jews from Auschwitz, though that was an ultimate result of D-Day. So B is out.
Since the question is asking the PURPOSE of D-Day, I think A is the best answer. D is more of a description of what D-Day WAS rather than an explanation of its PURPOSE.
All I would know on this matter, is : America joined WWI because of the American lives being lost on Passenger liners such as the RMS Lusitania.
For the First Crusade the main goal was to halt the spread of Muslim rule
