Passage Summary: Geothermal energy is cheaper than coal or gas in the few places we can currently reach it, and supporters believe it will soon be affordable everywhere.

Conclusion: Geothermal power will likely become an economically viable energy source in most regions in the near future.

Reasoning: While currently limited to specific geographic areas where hot water is easily accessible, geothermal energy is already more cost-effective than fossil fuels in those locations.

Analysis: To strengthen the advocates' claim, we need to bridge the gap between 'currently limited' and 'available in most areas.' Look for an answer that provides a mechanism for this expansion, such as a breakthrough in drilling technology that allows us to reach deeper, hotter rock in more locations. Since the current success is based on proximity to heat, the argument is bolstered if that proximity becomes less of a technical barrier. We are essentially looking for a reason why the 'near future' will look different from the present.