This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
A 60-year-old man is diagnosed to be suffering from Legionnaires' disease after he returns home from attending a convention. He could have acquired it: 
Select and explain. 
A. From a person suffering from the infection while travelling in the aeroplane, B. From a chronic carrier in the convention center, C. From inhalation of the aerosol in the air conditioned room at convention center, D. By sharing an infected towel with a fellow delegate at the convention
C: From inhalation of the aerosol in the air conditioned room at convention center
Answer: C: From inhalation of the aerosol in the air conditioned room at convention center 
Explanation: Infection normally occurs after inhaling an aerosol (fine airborne paicles) containing Legionella bacteria. Potential sources of such contaminated water include cooling towers used in industrial cooling water systems as well as in large central air conditioning systems. Note - Transmission to humans occurs when aerosols are created in manmade water supplies that harbor Legionella. Most outbreaks have occurred in or around large buildings such as hotels, factories, and hospitals with cooling towers or some other pa of an air-conditioning system as the spreading vehicle. Ref: Textbook of Microbiology By Ananthanarayan and Panicker, 6th Edition, Page 377 ; C.G., Ryan K.J. (2010). Chapter 34. Legionella. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.