The correct answer is D. Natural gas.
Natural gas is a fossil fuel formed when ancient plants and animals were buried and subjected to intense heat and pressure over millions of years. It is a non-renewable resource, meaning that it cannot be replaced once it is used up. Natural gas is a clean-burning fuel that produces fewer emissions than other fossil fuels, such as coal and oil. It is also a versatile fuel that can be used to generate electricity, heat homes and businesses, and power vehicles.
Agricultural waste is a renewable resource that can be used to generate energy. However, it is not a commercial source of energy because it is not widely used or traded. Dried dung is a renewable resource that can be used to generate energy. However, it is not a commercial source of energy because it is not widely used or traded. The sun is a renewable source of energy, but it is not a commercial source of energy because it is not yet possible to capture and store its energy on a large scale.
In conclusion, the correct answer is D. Natural gas.