题目

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   答案：B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’。18．如图是一个程序框图，则输出的S的值是63．