Which of the following statements is LEAST supportive of the idea that genetic exchange between bacteria occurs in the human gastrointestinal tract?

A) the high bacterial cell density in this environment
B) the presence of mixed species and biofilms in this environment
C) the presence of dead bacteria as a source of extracellular DNA for transformation
D) the passage of antibiotic resistance genes from one bacterium to another within a patient
E) the presence of pseudogenes in bacteria