Patients with an X-Linked Inherited Disease Called Hyper IgM (XHIGM)syndrome

Patients with an X-linked inherited disease called Hyper IgM (XHIGM) syndrome have a deficiency in CD40 ligand,a protein found on the surface of T lymphocytes.Patients with XHIGM are unable to make the class switch between IgM and either IgA or IgG.From this information,you could conclude that:

A) B-cell production of IgM does not depend on the CD40 ligand.
B) the class switch between IgM and either IgA or IgG requires T cells.
C) the switch between membrane-bound IgM and secreted IgM requires T cells.
D) B-cell production of IgM does not depend on the CD40 ligand,and the class switch between IgM and either IgA or IgG requires T cells.