In paragraph 6, the author implies that in California, Hawaii, the Philippines, Japan, Mexico, and the rift valleys of Africa the potential size of the geothermal resource is so large that A. it might be economically worth developing these sites even though geothermal energy is not renewable B. these sites will be the first geothermal energy sites to be developed with new technology C. these sites are likely to make a large-scale contribution to the world energy budget in the twenty-first century D. it does not matter whether they have naturally occurring deposits of hot water or steam