Which of the following is true?

a.
the synergy between myc and bcl-2 results from the fact that myc is a potent oncogene and bcl-2 disables p53 -mediated apoptosis

b.
pro- and anti-apoptotic proteins control the release of caspases from the mitochondria.

c.
tumor cells express elevated levels of p53 protein because of chromatin remodeling of the p53 promoter region

d.
because apoptosis occurs normally during development and morphogenesis, p53 -/- mice are embryonic lethal.