Calorific Value:
Calorific value is the amount of heat energy released per unit mass of a substance when it is completely burned. It is typically measured in units of joules per gram or kilojoules per kilogram.

Petrol:
- Petrol, also known as gasoline, is a fossil fuel commonly used as a fuel in internal combustion engines.
- It is derived from crude oil through a refining process.
- The calorific value of petrol is approximately 44 megajoules per kilogram (MJ/kg).

Coke:
- Coke is a solid carbonaceous material that is derived from coal.
- It is used as a fuel and in the production of steel.
- The calorific value of coke is typically around 24-35 MJ/kg.

Natural Gas:
- Natural gas is a fossil fuel composed primarily of methane.
- It is commonly used for heating, cooking, and electricity generation.
- The calorific value of natural gas is approximately 55-56 MJ/kg.

Kerosene:
- Kerosene is a flammable hydrocarbon liquid that is commonly used as a fuel in jet engines, lamps, and heaters.
- Its calorific value is typically around 46-48 MJ/kg.

Comparison:
- From the given options, natural gas has the highest calorific value of approximately 55-56 MJ/kg.
- It is important to note that the calorific value can vary depending on the composition and quality of the fuel.
- Natural gas has a higher calorific value compared to petrol, coke, and kerosene.
- This means that natural gas releases more heat energy per unit mass when it is burned, making it a more efficient fuel in terms of energy production.

Overall, natural gas is the option with the highest calorific value among petrol, coke, natural gas, and kerosene.