Genetically knocking out both copies of the p53 gene in rats:
a) results in lower malignancy rates, but rates are otherwise seemingly normal.
b) has no effect unless the rats live outside the laboratory and are exposed to environmental stress.
c) increases cell death by apoptosis, leading to developmental defects.
d) results in higher rates of cancer onset, but the rats are otherwise seemingly normal.
e) is embryonic lethal.