I agree that I too am surprised that an intelligent person couldn't pick out the one claimed to be correct.
But the three answers to the question itself were obviously the product of a researcher who didn't understand the March or its issues.
Whilst Palmers closure was undoubtedly the catalyst, the final straw as it were, the March was against Poverty and Unemployment brought about by the progressive loss of the Mines heavy industry and the worldwide depression.
The causes were far too broad to be trivialised into three one word answers.
But hey. I like the Chase.........!!