The correct option is B Coal
Inexhaustible resources are the natural resources that have an endless supply. Coal has limited reserves and is a depleting resource. Coal and petroleum were formed from the degradation of biomass millions of years ago and hence these resources will be exhausted in future no matter how carefully we use them. Various estimates show that with the present rates of usage, our known petroleum resources will last for about forty years and the coal resources for about two hundred years.