SCID Is Defined by a Lack of Functional B and T

SCID is defined by a lack of functional B and T cells which eliminates protection by humoral and cell-mediated immunity. Which of the following is true?

A) A genetic defect disrupts the development of the lymphocytic cell lines.
B) A genetic mutation renders the individual incapable of removing a toxic DNA metabolite from lymphocytes, which ultimately destroys them.
C) Genes coding for B and T cell receptors are mutated so the cells are incapable of binding antigens.
D) Genes that code for interleukin receptors are mutated so the individual's B and T cells do not receive the activation signals, rendering them useless.
E) All of the choices describe cases of SCID.