1. A man takes a roll of dollar bills out of his pocket and "peels" off a few to pay the restaurant tab. Each time he peels, he wets his thumb with saliva. What is the hazard involved? {3.5} 2. In the beginning of chapter-20 you learned that for many diseases, a penetration of the mechanical barriers surrounding the human body must take place. Can you think of any disease where penetration is not a prerequisite to illness? {3.5} 3. A woman takes an antibiotic to relieve a urinary tract infection caused by Escherichia coli. The infection resolves, but in two weeks, she develops a Candida albicans ("Yeast") infection of the vaginal tract. What conditions may have caused this to happen?{3.0}