How can normal flora be a barrier to entry?

A. They activate the complement system, which punches holes in the invading pathogen.
B. They use up nutrients and release wastes, preventing pathogenic bacteria from gaining a foothold.
C. They cause an inflammatory response that kills pathogenic bacteria upon contact.
D. They release histamine, which causes blood vessels to become permeable.
E. They phagocytize any pathogenic bacteria that attempt to infect.


Answer: B

Biology & Microbiology

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