In 1983, when oil prices were still high in my area, I installed a ground-s

游客2023-11-21 67

问题    In 1983, when oil prices were still high in my area, I installed a ground-source heat pump in my brand-new, well-insulated, 1,600-square-foot house. It cost several thousand dollars more than comparable systems that use oil, gas or wood, but I figured I’d recover my higher initial expense m a few years through lower energy bills.
   True, my heat pump runs on electricity -- an expensive commodity where I live. But most of its energy comes from the earth, a propylene-glycol solution circulates through 1,200 feet of two-inch-diameter plastic pipe buried three feet deep in a field next to my house. As it travels, the solution absorbs heat from the surrounding soil, even when soil temperature drops below freezing.
   My ground-source heat pump also offers important benefits that have nothing to do with economics.
-- Minimal fire hazard -- no chimney, firebox, or heating elements -- only pumps, fans, and a compressor.
-- Cleanliness -- no combustion products, thus no chance of my heating system polluting the indoor air, leaving scummy deposits on walls and furniture.
-- Reliability -- solid-state electronic controls and sealed bearings almost eliminate breakdowns.
-- No maintenance -- no wood to cut, ashes to haul, or chimney to clean.
-- Convenience -- The system runs automatically, even switching from heating to air conditioning as needed. I can simply lock the door and go away for a day, week or month.
   Not only did I expect to start saving on energy costs immediately, but I also expected those savings to grow over the years as oil prices continued to soar. Since I was wrong about oil prices, the big dollar savings I’d hoped for haven’t materialized. Nevertheless, I am satisfied, all things considered. [br] One benefit the author mentions is that the system ______

选项 A、uses no electricity
B、has a fire-safety shutoff
C、docs not pollute the air in the house
D、requires less insulation in house walls

答案 C

解析本题询问该系统的优点。文中列举了五个优点，并有记号一一标出。与原文相比可知，只有C项是属于优点之一的，原文为“Cleanliness—no combustion products， thus no chance of my heating system polluting the indoor air"。

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