—Fire is very useful to human! —Yes, especially in winter a fire _____________warmA.used to keepB.can be used to keepC.is used to keepingD.was used to keeping
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B解析考查固定用法。used to do，过去常常，现在已不再如此；be used to do sth.被用于做某事；be used to doing sth.习惯于做某事。根据句意，应是火被用来取暖。所以选B。