Introduction:
Cooking is an essential activity for all households. In the past, people used to cook food using traditional methods such as burning wood, coal, or dried animal dung. However, with the advancement of technology, a variety of fuels are available for cooking purposes.

Answer:
The most commonly used fuel for cooking nowadays is gas or electricity. Kerosene oil is still used in some rural areas where gas or electricity is not available, but its usage is decreasing day by day due to its adverse effects on health and the environment. Coal is not used for cooking purposes in households, as it is mainly used in industries for power generation.

Advantages of using gas or electricity for cooking:
1. Convenience: Gas or electric stoves are easy to use and provide instant heat, making cooking faster and more efficient.
2. Safety: Gas or electric stoves are safer than traditional cooking methods, as there is no risk of fire or smoke inhalation.
3. Cleanliness: Gas or electric stoves are cleaner than traditional cooking methods, as there is no ash or residue left behind.
4. Cost-effective: Gas or electricity is a cost-effective option for cooking, as it is easily available and affordable.

Disadvantages of using gas or electricity for cooking:
1. Dependence on infrastructure: Gas or electric stoves require infrastructure such as gas pipelines or electricity connections, which may not be available in some areas.
2. Power outages: In case of power outages, electric stoves become useless, and gas stoves may become dangerous if not handled properly.
3. Initial installation cost: The initial installation cost of gas or electric stoves may be higher than traditional cooking methods.
4. Environmental impact: The use of gas or electricity for cooking has an environmental impact, as it requires the burning of fossil fuels.

Conclusion:
In conclusion, gas or electricity is the most commonly used fuel for cooking purposes nowadays due to its convenience, safety, cleanliness, and cost-effectiveness. However, it is essential to consider the disadvantages of using these fuels, such as dependence on infrastructure, power outages, initial installation cost, and environmental impact.