34. Which of the following statement about severe combined immunodeficiency (SCID) is NOT true? (A) Defects in T-cell development can result in severe combined immunodeficiencies. (B) X-linked SCID is the most frequent form of SCID. (C) X-linked SCID is caused by mutations in the gene interleukin 2 receptor subunit gamma on the human X chromosome. (D) Natural killer cells develop normally in humans with X-linked SCID.