31. The Rb gene in retinoblastomas is similar to the Apc gene in polyposis colon carcinomas in that both genes ______.

(1) are tumor suppressors

(2) are in a locus that shows loss of heterozygosity in the hereditary form of the cancer 

(3) should be inactivated in both copies to cause the nonhereditary form of the cancer

(4) are mutated in one copy in all cells of patients with a hereditary form of the cancer
(A) (1) only.
(B) (1), (2), (3).
(C) (2), (4).
(D) (1), (3), (4).
(E) (1), (2), (3), (4).