The function of IgD on the surface of B cells is to:

a) present antigen to helper T cells.

b) present antigen to cytotoxic T cells.

c) bind antigen so that it can be internalized by the B cell and presented to helper T cells on class II MHCs.

d) bind antigen so that it can be internalized by the B cell and presented to cytotoxic T cells on class I MHCs.