单项选择题What was the Cabbie doing when I took his taxi? A. He was writing a letter. B. He was looking out of the window. C. He was reading a book. D. He was reading a letter.
单项选择题自动闭塞区间通过信号机显示停车信号，停车等候()分钟，信号机仍未显示进行信号时，如确认前方闭塞分区内有列车时，不得进入。
