Read the following passage and answer the question :

Use of Non-conventional sources of Energy : India, as you know, is hugely dependent on thermal & hydro power plants to meet its power needs. Both of these have adverse environmental impacts. Thermal power plants emit large quantities of carbon dioxide which is a green-house gas. It also produces fly ash which if not used properly, can cause pollution of water bodies, land & other components of the environment. Wind power & solar rays are good examples of non conventional cleaner & greener energy sources but they are not yet explored on a large scale due to lack of technological devices.

Identify the Non-conventional source of Energy.

Solar Energy

The correct answer is option (4) : Solar Energy

The passage refers to solar rays as one of the examples of non-conventional but cleaner and greener energy sources.