Is Simple Hygiene a Key to Stopping Infectious Diseases

Is simple hygiene a key to stopping infectious diseases?

A) Yes, pathogens grow better in unsanitary conditions.
B) Yes, you can avoid taking in and passing around pathogens by washing your hands frequently and keeping your bodily fluids to yourself.
C) Yes, there are no pathogens in clean conditions.
D) No, it helps, but not all that much because bacteria are everywhere.
E) No, because if you manage to sterilize yourself, the good bacteria are no longer there to keep the bad bacteria at bay.