A nurse is providing care for a 17-year-old boy who has experienced recurrent sinus and chest infections throughout his life and presently has enlarged tonsils and lymph nodes. Blood work indicated normal levels of B cells and free immunoglobins but a lack of differentiation into normal plasma cells. The boy is currently receiving intravenous immunoglobulin (IVIg) therapy. What is the boy's most likely diagnosis?
a) Common variable immunodeficiency (CVID)
b) Severe combined immunodeficiency (SCID)
c) X-linked agammaglobulinemia (XLA)
d) Wiskott-Aldrich syndrome (WAS)