The fallacy is that you won't believe your biology teacher because she used to be an alcoholic over a commonly known fact. People can change, and this is proven by the fact that the word "used" is in the sentence. "Heard" is seen as well, meaning that you don't know for sure. Besides that, it is widely known that you should wash your hands to prevent the spreading of germs.
Its A, for example when the author mentions a phenix in the book Fahrenheit 451, it is a symbol of the rebirth of ideas that will soon come, not a literal phoenix.
