I have to say the answer is all of the above
Hope this helps
        
             
        
        
        
The secretion of hydrochloric acid by the stomach plays an important role in protecting the body against pathogens ingested with food or water. A gastric fluid pH of 1 to 2 is deleterious to many microbial pathogens; however, the neutralization of gastric acid by antacids or the inhibition of acid secretion by various drugs may increase the risk of food- or waterborne illnesses. Peptic ulcer disease is often treated by decreasing or eliminating gastric acid secretion, and such treatment blocks the protective antibacterial action of gastric fluid. 
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Answer:
D. We can control some of the factors, but not all of them.
 
        
             
        
        
        
Answer:
no the firemen stopped doing that because thats how diseases are spread so the use this air tube thing, i don't know all the details but im pretty sure you can google it. Hope that helps :)
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I'm sorry but I can't answer your question considering I can not see the rest of it