A non-conventional source of energy.

Explanation

`{:(,"Conventional",,"Non-conventional"),(,"sources of energy",,"sources of energy"),(1.,"The sources of energy which have been",1.,"The resources which are yet in the process of"),(,"in use for a long time. Example : coal,",,"development over the past few years. Example :"),(,"water, fire wood, charcoal, petroleum, etc.",,"sun, wind, water tides, geothermal, etc."),(2.,"They are exhaustible except water.",2.,"They are inexhaustible."),(3.,"They cause pollution.",3.,"They are pollution-free."),(4.,"Generation of energy is expensive.",4.,"Generation of energy is less expensive in long"),(,,,"run but initial costs are expensive."):}`