Which resource is both renewable and inexpensive?

A resource is a source or supply from which a benefit is produced. Resources can be broadly classified upon their availability they are renewable and non renewable resources.

Renewable Resources :: A resource that can be replenished after use are known as Renewable resources.

Examples :: Sunlight, Water, biomass,...

Non renewable Resources :: A resource that, once used, is no longer available are known as Non renewable Resources. 

Example :: Coal, fossil fuels, natural gas,...

Sunlight is the both renewable and inexpensive resource from the given options.