In a 100 kg afebrile person with intact skin, the insensible fluid loss from the lungs and skin is approximately 500 mL/day (Option A).
Insensible fluid loss refers to the water that is lost from the body through evaporation, primarily from the lungs during respiration and from the skin through perspiration. This loss is not easily measurable and occurs continuously throughout the day.
In a person with normal body temperature (afebrile) and intact skin, the average insensible fluid loss is estimated to be around 500 mL per day. This loss helps maintain the body's fluid balance and temperature regulation.
It's important to note that this estimation can vary depending on various factors such as ambient temperature, activity level, and individual variations. However, in the given context, the most appropriate and accurate answer is Option A: 500 mL/day.