The effective temperature of ‘comfort zone’ is
**Core Concept**
The comfort zone, also known as the thermoneutral zone, is the range of temperatures within which the human body can maintain its optimal metabolic rate without excessive heat loss or gain. This zone is crucial for thermoregulation, and its boundaries are influenced by factors such as age, sex, and acclimatization.
**Why the Correct Answer is Right**
The effective temperature of the comfort zone is typically around 22°C (71.6°F) to 25°C (77°F), with a relative humidity of 40% to 60%. This range allows for efficient heat transfer through radiation, conduction, and convection, minimizing the need for sweating or shivering. The human body's ability to maintain its core temperature within this zone is mediated by the hypothalamus, which regulates sweating, vasoconstriction, and other thermoregulatory mechanisms.
**Why Each Wrong Option is Incorrect**
**Option A:** 18°C (64.4°F) is too cold for the comfort zone, as it would require increased metabolic rate and vasoconstriction to maintain core temperature.
**Option B:** 28°C (82.4°F) is too hot, as it would lead to increased sweating and potential heat exhaustion.
**Option C:** 35°C (95°F) is extremely hot, and the human body would struggle to maintain its core temperature within this zone.
**Clinical Pearl / High-Yield Fact**
The comfort zone is essential for maintaining optimal physical and mental performance, and deviations from this zone can lead to heat-related illnesses or hypothermia.
**Correct Answer:** C. 25°C (77°F)