A and C are both correct to a degree. He is well known for his peculiar geometric forms in his paintings, which were not at all realism, but rather a style called cubism. During his Blue Period, his paintings were literally painted in blues, and were true to the answer in C. One particular painting depicts an elderly man playing a guitar with a frown on his face looking incredibly sad and upset. I would probably select C because it describes his Blue Period in contrast to his typical style, which is described in A.
I think this is what you wanted for an answer!..
