The options given in (a) and (b) are the same. The Renewable sources of energy are also known as inexhaustible sources of energy and Non-renewable sources of energy are also called exhaustible sources of energy.

(i) Renewable sources of energy /Inexhaustible sources: Those sources of energy which are abundant in nature and can be used again and again. These sources never get exhausted. For example, wood, water etc.

(ii) Renewable sources of energy/Exhaustible sources: Those sources of energy which have accumulated in millions of years and cannot be produced in very less time span. For example, coal. If all the coal gets used up completely, it cannot be produced quickly in nature.