[单项选择]使用自动闭塞法行车时，遇由未设出站信号机的线路上发车，行车凭证为（）。
A. 路票
B. 绿色许可证
C. 红色许可证
D. 调度命令

“Down-to-earth”means someone or something that is honest. realistic and easy to deal with. It is a pleasure to find{{U}} (31) {{/U}}who is down-to-earth. A person who is down-to-earth is easy to talk{{U}} (32) {{/U}}and accepts other people as equals. A down-to-earth person is just the{{U}} (33) {{/U}}of someone who acts important or proud.
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