You Are an RN Working in the Emergency Department (ED)

You are an RN working in the emergency department (ED) at a major hospital in New York City. During one shift, you see two patients who are exhibiting coughing with blood-containing sputum, and shortness of breath. Both patients report that they have experienced headaches, muscle aches, high fever, confusion, and shaking chills in the days preceding their ED visit. One of the patients also has some digestive tract symptoms including diarrhea, abdominal pain, and vomiting. You discover that the patients live in the same apartment building, although they do not know each other. You suspect that they have a type of pneumonia, and given the circumstances, think it may be legionellosis. You read up on this disease to refresh your memory about it.
-What is the likely source of the L. pneumophila in this case?

A) The cooling water tower providing feeding airconditioners in the patient's offices. 
B) The showers or faucets at the local gym where both patients regularly worked out.
C) The produce section at the grocery store where vegetables are sprayed with water for freshness.
D) The water tank in the patient's building that provides hot water to apartments.
E) Further investigation by an agency such as the CDC would be needed to determine this.