Which of the following is not a technology that can be used to conserve resources?
a. hydropower
b. volcanic power
c. natural gas
d. geothermal

c. natural gas 

A renewable resource is a substance of economic value which can be replenished or replaced either through natural recurring processes or biological reproduction.

Biomass is a biological material taken from plants or plant-based materials.

Biomass is considered a renewable resource because plants and plant-based materials can be found everywhere and once used these plants will continue to grow and supply the demand for biomass consumption.