You Are a Nurse on a Post-Surgical Ward

You are a nurse on a post-surgical ward. One of your patients is an elderly woman who has just had her gallbaldder removed. When you go into her room to check on her, you find that she has significant diarrhea, as well as fever and abdominal pain. You suspect that she has Clostridium difficile infection (CDI) , and send a sample of her feces down to the hospital lab for analysis. The test result indicates that your patient does indeed have CDI. You make your patient comfortable and answer her questions about her illness.
-Your patient wonders how she contracted CDI. Which of the following would be a good explanation for her?

A) She is elderly; elderly people frequently develop gastrointestinal complaints such as CDI. It is to be expected in an aging person.
B) She has been on antibiotic therapy because of her surgery. The antibiotics disrupted her normal intestinal microbiota, allowing any C. difficile present to flourish.
C) C. difficile is usually a community-acquired organism. She most likely came to the hospital already infected with it but it takes several days for signs and symptoms of CDI to appear.
D) Most surgical equipment is contaminated with C. difficile endospores, which are ubiquitous. Most likely your patient acquired CDI directly from her surgery. 
E) Nobody knows how people contract CDI. The causative bacterium is a common environmental organism and it is not known how it becomes pathogenic.