Our teacher is always busy preparing lessons until 11 o’clock at night, we stude
来源：网络
时间：
推荐文章
Our teacher is always busy preparing lessons
until 11 o’clock at night, _______we students have gone to sleep.
A. that time B. by which time C. by that time D. which time
试题答案
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’。