I arrived home at midnight, _______ my parents had been waiting for nearly three hours.A.at that timeB.by that timeC.at which timeD.by which time
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D解析这题考查介词和非限制性定语从句，从句式结构看这是非限制性定语从句，又根据从句的时态：过去完成时，可以判断是by，所以填by which time。选D。句意是：我午夜到家，到那时为止我父母已经等了近3小时了。