ANS:A - coke

Coke is a type of fuel derived from coal through a process called carbonization. It is produced by heating coal in the absence of air to drive off volatile compounds and moisture, leaving behind a porous, hard, and nearly pure form of carbon. Coke has several properties that make it suitable for use as a heat source in cupola furnaces:

1. High Carbon Content: Coke consists primarily of carbon, which allows it to burn at high temperatures without producing a significant amount of smoke or volatile gases.
2. Porous Structure: The porous structure of coke provides a large surface area for combustion, allowing for efficient heat generation.
3. Low Volatile Content: Coke has a low volatile content compared to coal, which means it produces relatively little smoke and ash during combustion, reducing air pollution and minimizing the buildup of impurities in the molten metal.
4. High Heating Value: Coke has a high heating value, meaning it releases a significant amount of heat when burned, making it suitable for melting metals in cupola furnaces.