Which of the Following Statements Best Explains the Continued Incidence

Which of the following statements best explains the continued incidence of infectious disease in the United States today?

A) Illness theory explains that there are many causes of illness resulting from environmental conditions.
B) No single theory adequately explains why a particular person gets a particular illness at a particular time.
C) The germ theory explains that a specific infection is caused solely by the invasion of particular bacteria.
D) The theory of susceptibility states that an individual only gets ill when there is extensive stress in his or her life.