四显示自动闭塞区段由未设出站信号机的线路上发出列车的行车凭证是（）
参考答案：绿色许可证
He stood up, the large door and looked outside. There on the ground lay a white dog.
A．opens
B．opened
C．opening
D．having opened
机动车仪表板上（如图所示）亮时，提醒驾驶人安全带插头未插入锁扣。
