Why might Mark Twain have written about lower-class citizens in his satires?

Why might Mark Twain have written about lower-class citizens in his satires?

A. to ensure that he wrote only about topics with which he was familiar.
B. to reflect the realities of life in his writings.
C. to ignore the upper class, which he did not see as being worthy of his attention.
D.to give readers a sense of what his life was like as a child.