A Physician Notices That Several Patients Are Infected with Clostridium

A physician notices that several patients are infected with Clostridium difficile, but only a few of the patients are symptomatic for disease. The reason for this discrepancy is

A) only those strains of the organism carrying the extrachromosomal DNA coding for the toxin gene will produce toxin and cause the individuals to be symptomatic.
B) only those strains of the organism carrying DNA coding for the toxin within its main DNA molecule will produce toxin and cause the individuals to be symptomatic.
C) the exotoxin produced contains only the nontoxic portion.
D) the exotoxin must be produced in conjunction with extracellular enzymes to cause problems.