Select the odd man out of the following, considering the commercial and non-commercial energy sources. 

The correct answer is  option 4):(Biomass)

Concept:

Commercial energy sources:

• The energy sources that are used to generate electricity and that are available in the marketplace at a specific price are known as commercial energy sources.
• The most commercialized forms of commercial energy sources are electricity, coal, natural gas and advanced petroleum products.
• The consumer has to  pay for commercial one
• These sources are used for business purposes

Non-commercial energy sources:

• Consumers need not pay for the Non-commercial resources
• These sources are generally renewable
• These sources cannot be used for business purposes 
• It is used for domestic purposes
• Eg: Biomass, Firewood