采用电话闭塞法组织行车，列车凭（）占用区间，司机以URM模式驾驶列车运行。
参考答案：路票
引起急性上呼吸道感染的主要病原为（）
A.细菌
B.病毒
C.真菌
D.原虫
E.螺旋体
All the essays _____________, the teacher sent the students home.
A．having written and collected
B．having been written and collected
C．being written and collected
D．to be written and collected
