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

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. Whereas, commercial sources are coal, petroleum, and electricity as they are bought and sold.