Answer:
because of something called mossillization
Answer:
both tolerance and withdrawal.
Explanation:
The answer for this question would be Integument, digestive, respiratory and urogenital.
The largest system that contact with the external environment would be integument and digestive. That makes two system has normal flora of microbes and not sterile like the other systems. Normal flora of microbes will prevent the pathogen microbe grows so it gives some benefit.
neurons are specialized cells that generate and conduct electrical impulses throughout the body.