Why Aren't Human Populations Evolving to Produce Immune Systems That

Multiple Choice

Why aren't human populations evolving to produce immune systems that are able to fight off MRSA and other "superbugs"?

A) because bacteria do not apply a selection pressure on human populations
B) because we do not have the mutations that would improve our immune systems
C) because the rate of human evolution is much slower than bacterial evolution
D) none of these
E) all of these