What is true about geothermal energy production worldwide?

A Because it is a new idea, very few countries are geothermal energy sources

B Only countries in the Southern Hemisphere are using geothermal energy on a large scale 

C Until the cost of geothermal energy becomes competitive, it will not be used globally

D Geothermal energy is already being used in a number of nations, but it is not yet a major source of power