OG6 阅读 Q47

Choice B is the best answer. The passage clearly states how two-sided solar panels will increase the efficiency of solar electricity units, explaining that they will be able to absorb excess reflected light, especially if those panels are built on sand: "That light reflects onto the back of the panels and could be harvested to increase the power output"(lines 61-62). 
Choices A, C, and D are incorrect because the passage explains only that two-sided solar panels can raise efficiency by harvesting reflected light, not that they can raise efficiency because they take little energy to operate (choice A), are cost-effective (choice C), or keep sunlight from reaching the ground (choice D).