The outer surface of body defenses is nonspecific, which means they do not attack specific pathogens. Skin is the very first immune system against nonspecific pathogens. Other than mucous membranes also act as a barrier to pathogens and produce chemical defenses.
Saliva also provides a non-specific external response as it contains mucus, antibacterial compounds and various enzymes to target bacteria and other pathogens.
B. Mutations cause a person's body cells to divide uncontrollably. There isn't a signal for cells to stop dividing, so this can cause cancer because cancer cells won't stop dividing without this signal.
