《素问·阴阳应象大论》中关于人体衰老的主要机制是（）
A. 体重，耳目不聪明
B. 阴气自半
C. 七损八益
D. 下虚上实
E. 气大衰
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液压伺服阀进油路安装的高压滤清器过滤精度一般为（）。
You need to perform a block media recovery on the tools01.dbf data file in the SALES database by using Recovery Manager (RMAN).Which two are the prerequisites to perform this operation？（）
A. You must configure block change tracking file
B. You must have first level 1 backups for RMAN to restore blocks
C. You must ensure that the SALES database is mounted or open
D. You must have full or level 0 backups for RMAN to restore blocks
E. You must take the tools01.dbf data file offline before you start a block media recovery
教师之间要“谦虚谨慎，尊重同志，相互学习，相互帮助，维护其他教师在学生中的威信。关心集体，维护学校荣誉，共创文明校风”。这是师德教育的()。
A. “双赢”协作原则
B. 和平共处原则
C. 自觉性原则
D. 实践性原则
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