Answer: C. Using only geothermal energy.
Explanation:
Sustainable practices are those practices which are done to utilize the natural resources in a manner so that they will remain available for the future generation too.
The use of geothermal energy is a sustainable practice this is because of the fact that it is obtain from the geosphere. It is an alternative source of natural energy. The geothermal energy is obtain from water released from a hot spring. The ground water is heated up by the hot mantle present in the earth core. The underground force and pressure liberates hot water. This form of energy can be used for heating up the buildings, constructing a natural water bath and for other uses. The utilization of this form of energy is suitable for the conservation of conventional resources like fossil fuels which are used for the generation of thermal energy. By this manner the conventional resources will be available for the future generation.
