The house, walls are red, is where my grandfather used to live ten years ago.A. whichB. of

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A. which
B. of which
(答案→)C. whose
D. that
解析：考查非限制性定语从句：句意：墙体是红色的房子是我祖父10年前住的地方。这是非限制性定语从句，先行词是the house，定语从句中的walls缺少定语用whose引导定语从句，名词+of which也可以引导定语从句，但是名词walls前面要加定冠词the，所以选C。