About 20% of the Human Population Has the Bacteria That

Multiple Choice

About 20% of the human population has the bacteria that causes childbed fever living on their skin, and yet death from it is very rare. Why?

A) People are now resistant to the bacteria.
B) The bacteria has evolved such that it never causes disease.
C) With all the antibacterial soaps available, most humans don't come in contact with bacteria.
D) The bacteria is only dangerous if it gets in the bloodstream and now it can be treated by antibiotics.
E) Doctors now routinely wash their hands.
"How do we know?"