Which of the following would be most likely to lead to cancer?
a. amplification of a proto-oncogene and inactivation of a tumor-suppressor gene
b. hyperactivity of a proto-oncogene and activation of a tumor-suppressor gene
c. failure of a proto-oncogene to produce a protein and amplification of a tumor-suppressor gene
d. hyperactivity of both a proto-oncogene and a tumor-suppressor gene
e. failure of both a proto-oncogene and a tumor-suppressor gene to produce proteins