Which of the following is an example of a "Non-Commercial" source of energy?

1. Cowdung cake
2. Coal
3. Firewood
4. Agricultural waste
5. Petroleum

A, C, and D

The correct answer is option 4: A, C, and D

Both commercial and non-commercial sources of energy are known as conventional sources of energy. Commercial sources are coal, petroleum and electricity as they are bought and sold. Non-commercial sources of energy are fuelwood, agricultural waste and dried dung. These are non commercial as they are not available in the market on a large scale.

There are three other sources of energy which are commonly termed as non-conventional sources — solar energy, wind energy and tidal power.