旅客不能按票面指定的日期、车次乘车时，应当在票面指定的日期、车次开车前办理一次提前或推迟乘车签证手续，特殊情况经站长同意可在开车后2小时以后办理。
气瓶水压试验有效期前（）应向气瓶检验机构提出定期检验要求。 ["一年","半年","1个月"]
Which two are features of IPv6?（） ["multicast","broadcast","allcast","podcast","anycast"]
持通票的旅客在中转站和列车上要求变更径路时，必须在客票有效期能够到达到站时方可办理。
Which two statements best describe spanning-tree BPDU processing for a blocking port？（） ["BPDUs that enter a blocking port are discarded.","BPDUs that enter a blocking port are processed.","Loopguard puts an interface into a loop-inconsistent state when BPDUs stop being received on a blocking port.","BPDUs are only processed on forwarding ports."]
教学过程认识说
