I arrived home at midnight, my parents had been waiting for nearly three hours.A. at that

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A. at that time
B. by that time
C. at which time
(答案→)D. by which time
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。