Your Father Has Just Been Diagnosed with Rheumatoid Arthritis

Your father has just been diagnosed with rheumatoid arthritis. He has pain and the sensation of "pins and needles" in some if his finger joints and also in his wrists. He knows you covered autoimmune diseases in your microbiology class, so asks you to help him understand his condition.
-You explain to your Dad that the causes of RA are not clear, but may involve all of the following EXCEPT

A) insufficient production of B cells, helper T cells, and cytotoxic T cells, so that the adaptive immune response is unable to differentiate "self" from "foreign."
B) infections-an immune response against a pathogen engaged in molecular mimicry may inappropriately attack healthy tissues as well. 
C) regulatory T cell problems-sometimes these cells are deficient or do not function properly; these cells play a role in regulating inappropriately activated lymphocytes.
D) genetics-RA is often seen in related people who share genes for major histocompatibility molecules.
E) These are all factors involved in developing RA.