Our teacher is always busy preparing lessons until 11 o’clock at night, _______we students have gone to sleep.A.that timeB.by which timeC.by that timeD.which time
网友回答
B解析句意为“我们的老师总是忙着备课到晚上11点钟，那时我们已经睡了”。by意为“到……时(为止)”，which time 指代 “11 o’clock at night’。