Mutations in two important cancer-critical genes, encoding p53 and Rb, respectively, are commonly found in cancers. What type of mutations are these expected to be?

A) Loss-of-function mutations in both genes
B) Loss-of-function mutation in p53 and gain-of-function mutation in Rb
C) Gain-of-function mutation in p53 and loss-of-function mutation in Rb
D) Gain-of-function mutations in both genes