Which of the Following Statements Are True of Resident Flora

Which of the following statements are true of resident flora (microbiota) ? (Read carefully and select all of the correct statements.)

A) The nasal cavities have a smaller flora than do the bronchioles.
B) Many of our resident flora prevent pathogens from establishing themselves.
C) Some colon flora produce vitamins that are useful to us.
D) The urinary bladder should have only a very small population, and the blood should be free of bacteria.
E) Resident skin flora include fungi as well as bacteria
F) Few pathogens reach the lungs, and those that do are quickly destroyed by red blood cells.