Why does Atticus accept Mrs. Dubose's cantankerous ways?

A.

Atticus knows Mrs. Dubose is in a lot of pain.

B.

Mrs. Dubose is Atticus's elder and he doesn't want to be disrespectful.

C.

Mrs. Dubose is an old friend of the Finch family.

D.

Atticus knows Mrs. Dubose is only kidding.