The skin is the first line of defense in preventing penetration by infectious agents. however, the skin can be bypassed. which of the following scenarios allows an infectious agent to enter the body without damaging the skin? a. a person is infected with malaria when a mosquito bite punctures his skin. b. a girl gets a staph infection when she falls and scrapes her knee. c. a boy is infected with rabies when a dog bites his leg. d. bacteria on food is ingested through the mouth.