Choice C is the best answer. In lines 10-17("A few years...he says"), the passage illustrates how the cost of solar energy has dropped in recent years: "A few years ago, silicon solar panels cost $4 per watt...'Now it's down to something like 50 cents a watt, and there's talk of hitting 36 cents per watt.'" In lines 44-47, the passage describes some of the new technology that exists in the field: "Meanwhile, researchers at the National Renewable Energy Laboratory have made flexible solar cells on a new type of glass from Corning called Willow Glass, which is thin and can be rolled up." Overall, the passage can be regarded as an objective overview of the solar panel industry delivered by a journalist covering the field.
Choices A and D are incorrect because the author does not present himself as either a consumer who plans to buy solar panels or a hobbyist with a personal interest in solar panel technology. Rather, the author focuses on developments in solar technology. Choice B is incorrect because the passage does not discuss research methods used in the solar panel field but rather the technologies that exist in the field.