溢流发生的原因是什么？
下列会计凭证中，属于自制原始凭证的有（）。 ["材料领料单","实存账存对比表","购货发票","印花税票"]
A customer has 4 POWER6 servers managed by a Hardware Management Console （HMC）. They plan to install a second HMC for redundancy. Which of the following statements correctlydescribes the dual HMC environment？ （） [" To provide the Service Agent function， both HMCs must have Service Agent enabled and a dedicated modem and phone line."," Authorized users must have the same username and password on both HMCs， so that every user of one HMC is automatically authorized on the other."," Both HMCs are automatically notified of any changes that occur in the managed systems， so results of changes made to the managed system by one HMC are visible on the"," Both HMCs must be running the same software revision. Software maintenance must be performed on both HMCs at the same time， but one HMC should be disconnected from"]
统计活动一般按照统计设计、统计调查、（）、统计分析和统计资料的开发利用这几个阶段依次进行。
以下哪种缺陷不是由于玻璃熔制时造成的（）。 ["线道","波筋","气泡","霞石"]
简述密钥的分类和作用。
