**Core Concept**
Heat stroke is a severe heat-related disorder characterized by the failure of the body's thermoregulatory mechanisms, leading to a significant elevation in core body temperature. This condition is distinct from heat cramps and heat exhaustion in its pathophysiology and clinical presentation.

**Why the Correct Answer is Right**
Heat stroke occurs when the body's ability to dissipate heat is overwhelmed, resulting in a core body temperature of 104°F (40°C) or higher. This is in contrast to heat cramps and heat exhaustion, which are caused by a milder heat stress response. In heat stroke, the hypothalamic thermostat is disrupted, allowing the body temperature to rise unchecked.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because heat cramps and heat exhaustion are both caused by heat stress, whereas heat stroke is a more severe condition.
**Option B:** This option is incorrect because heat exhaustion is a milder condition that is often characterized by a lower core body temperature and a more gradual onset.
**Option C:** This option is incorrect because heat cramps are typically caused by a loss of electrolytes and fluids, rather than a failure of the body's thermoregulatory mechanisms.

**Clinical Pearl / High-Yield Fact**
Heat stroke is a medical emergency that requires immediate attention, as it can lead to severe brain damage, organ failure, and even death if left untreated.

**Correct Answer: D.**