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
Which of the following is a method for acquiring infection by Legionella pneumophila ? 
Select and explain. 
A. Consumption of contaminated water with protozoa of legionella, B. Breathing aerosols of environmental water sources such as air conditioning units, C. Consumption of contaminated meat and meat products, D. Close contact with carriers of legionella
B: Breathing aerosols of environmental water sources such as air conditioning units
Answer: B: Breathing aerosols of environmental water sources such as air conditioning units 
Explanation: Ans. is 'b' Inhalation of aerosols containing ligionella is no more considered common mode of transmission of legionella. Aspiration is the most common mode of transmission of legionella. Earlier the most popular theorey was that organism is aerosolized in water and people inhale the droplets containing legionella. However, new evidence suggests that another way of contracting legionella is more common. Aspiration now appears to the most common mode of transmission of legionella.