关于1850TSS-320的正确描述有（） ["320G通用交换能力","16个全高度槽位\/32个半高度槽位","1+1通用矩阵、1+1控制板、1+1电源备份"]
以下有关公务的说法正确的是（） ["某OTM站线路光缆断了，业务中断，但公务电话还能通，因为OSC信道是有保护","话机上的铃流开关“RING”应打在“ON”位置","拨号方式开关应打在“T”位置，即双音多频拨号方式","公务电话在不通话时应处在挂机状态"]
班级中的学生角色由性别、成绩、班级组织中的职务等三种因素组成。
足球比赛中，防守一方踢或触球，使球的整体从本方端线越出时，应由对方队员踢罚（）恢复比赛。 ["任意球","角球","球门球","界外球"]
Which three statements about bidirectional PIM are true？（） ["Traffic for a bidirectional group flows along the one shared tree and simultaneously utilizes multiple paths in a redundant network topology","It does not require any traffic signaling in the protocol","Membership to a bidirectional group is signaled using explicit Join messages","It maintains source-specific forwarding state","It reduces memory， bandwidth， and CPU requirement"]
谁为光作见证？
