问题
选择题
I arrived home at midnight, _______ my parents had been waiting for nearly three hours.
A．at that time
B．by that time
C．at which time
D．by which time
答案
答案：D
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。