A. Power: Energy: Power is the rate at which energy is used or produced. This is a broader relationship but does not have the same specific source-to-type relationship as coal to thermal energy.
B. Bulb: Light: A bulb produces light, but it doesn’t represent a source that specifically generates a type of energy, as in the coal-to-thermal relationship.
C. Air: Atmosphere: Air is a component of the atmosphere, but this does not relate in the same way as coal provides thermal energy.
D. Water: Hydel: Water is used in hydropower (hydel) to generate electricity, specifically through thermal energy conversion. This closely parallels the relationship between coal and thermal energy, as both are sources for a specific type of energy production.The correct option is (C): Doctor : Sickness