Which one of the following clients is most susceptible to the development of Legionnaire's disease? A. 21-year-old college freshman who lives in a dormitory B. 35-year-old automobile salesman who works outside C. 55-year-old teacher who frequently travels abroad D. 60-year-old coal miner who has a 2 PPD smoking history

Legionnaire's disease is a severe form of pneumonia caused by Legionella bacteria. The risk factors that make a person more susceptible to developing the disease include: - Age (being over 50 years old) - Smoking - Chronic lung conditions - Weakened immune system - Certain environments (such as hotels, hospitals, or buildings with complex water systems)

A. 21-year-old college freshman who lives in a dormitory: While living in a dormitory may expose this person to complex water systems, they are young and unlikely to have a weakened immune system or chronic lung conditions. B. 35-year-old automobile salesman who works outside: This person is also relatively young and primarily works outdoors, rather than in an environment with complex water systems. C. 55-year-old teacher who frequently travels abroad: This person is over 50 and frequently exposed to environments like hotels that may house Legionella bacteria. However, their profession does not indicate smoking or other risk factors. D. 60-year-old coal miner who has a 2 PPD smoking history: This person is over 50, works in an environment that potentially exposes them to poor air quality, and has a significant smoking history, all of which could contribute to the development of Legionnaire's disease.

Option D, the 60-year-old coal miner with a 2 PPD smoking history, has the highest number of risk factors for developing Legionnaire's disease. This person's age, smoking history, and work environment all make them more susceptible to the illness compared to the other options presented.