Answer: Uncertainty
Explanation:
The principle of science used here is uncertainty. The various doctors attributed their sickness to hookworm gotten from cat and dogs but the uncertainty here is that it wasn't described they had access to the water because they were disappointed by the feces of dogs and cat found around, and how they all got the same rashes at the same time is questionable
The first line of defense of the immune system includes mechanical barriers that prevent organisms from the body. The second line of defense includes processes that help remove or neutralize organisms that have penetrated mechanical barriers. The third line of defense is a complex defense that recognizes and reacts to specific organisms.
