The Grapes of Wrath is a movie that centers on the psychological disorder- depression. The factors that made Muley Graves be touched or half-mad were, first, the land that has been meaningful for him and his family was sold to the Shawnee Land and Cattle Company and second was they had to leave their home.
You could argue that this is an indication of Walter Cunningham's severe poverty. He is very poor, and poor people did not have access to sweets or treats such as molasses syrup, so when he was offered it he deemed it appropriate to drench his entire lunch in it.
I think that the only right option is c. Workers had easier jobs and shorter hours. It caused lower quality of production