Which relative humidity level is described as impairing the body's ability to evaporate sweat to cool itself?

Which relative humidity level is described as impairing the body's ability to evaporate sweat to cool itself?

• A. Humidity level that stops evaporation
• B. Humidity level that impairs evaporation
• C. Humidity level that reduces evaporation rate
• D. Humidity level that enhances cooling

Answer: (B)

Evaporative cooling relies on sweat evaporating from the skin to transfer heat away from the body. As relative humidity increases, the air already contains a lot of water vapor, so the vapor pressure gradient between the skin and the surrounding air decreases. That makes evaporation harder, or impaired, which reduces the body’s ability to cool itself. The phrase describing a humidity level that impairs evaporation directly captures this effect—the evaporation process is hindered, not necessarily stopped, and cooling is diminished. The other phrasings either imply an absolute stop, a more specific reduction in rate, or even an enhancement of cooling, which doesn't align with how high humidity actually affects sweating and heat loss.

Evaporative cooling relies on sweat evaporating from the skin to transfer heat away from the body. As relative humidity increases, the air already contains a lot of water vapor, so the vapor pressure gradient between the skin and the surrounding air decreases. That makes evaporation harder, or impaired, which reduces the body’s ability to cool itself. The phrase describing a humidity level that impairs evaporation directly captures this effect—the evaporation process is hindered, not necessarily stopped, and cooling is diminished. The other phrasings either imply an absolute stop, a more specific reduction in rate, or even an enhancement of cooling, which doesn't align with how high humidity actually affects sweating and heat loss.