Answer:
a. Limited to certain regions.
Step-by-step explanation:
It will be wrong to say that the earth is not hot enough, geothermal energy is intermittent or this source is not enough to generate electricity. It is not the fuel, it's the earth which is continuously emitting radiation or heat and it will keep on emitting that. So it's the most consistent source of energy and is abundant enough to produce electricity. So the problem is, it's the location specific source of energy and can only be utilized at the places lying at the edges of the tectonic plates. So the correct option is a.