Which group of individuals would most likely be affected by lower air density at high altitudes?

Athletes would most likely be affected by lower air density at high altitudes because the reduced air pressure results in a decrease in the amount of oxygen available for breathing. This can lead to decreased athletic performance, as muscles require oxygen for energy production during physical activity. At high altitudes, athletes may experience symptoms of altitude sickness, such as headaches, fatigue, and difficulty in maintaining endurance.

While surgeons, elephants, and accountants may also feel some impact from changes in air density, they are not typically engaged in physically demanding activities that require immediate and sustained oxygen intake like athletes. Surgeons work in controlled environments and might not be at high altitudes during surgery, elephants, as large animals adapted to various environments, are less sensitive to these conditions, and accountants perform sedentary tasks that do not require significant aerobic exertion. Thus, the most pronounced effects on performance and well-being in a high-altitude environment are felt by athletes.