In which of the following heat related illnesses has the individual lost the ability to lose heat through the mechanism of sweating?

Correct Answer: Option C — Heat stroke

Heat stroke is a medical emergency characterized by the failure of the body's thermoregulatory system. When the hypothalamus ceases to function effectively, the body loses its ability to dissipate heat through evaporation, leading to a dangerous rise in core temperature that requires immediate cooling and medical intervention.