为使通信卫星能够尽可能的覆盖地球的全部面积，最少需要（）同步定点通信卫星。
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理想与现实本来就是一对矛盾，二者是对立统一的关系。其中，统一性体现在哪里？
What does the Fast Connection Failover feature of Active GridLink for RAC provide?（）
A. instant notification of a RAC node failure so applications never have to retry a transaction that was sent to a node that failed during the transaction
B. near-instant notification of the failure of a RAC node failure that minimizes the possibility connection to a failed node being provided to an application
C. application level notification of a failed RAC node such that an application can retry a transaction if required
D. faster failover for Multi Datasources
E. guaranteed transaction high availability when interacting with an Oracle RAC Database
程变更的内容包括（）
A. 设计变更
B. 施工条件变更
C. 进度计划变更
D. 新增（减）工程项目内容
E. 施工人员变更
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