铁路用地应按地界线上埋设（），地界桩制作和埋设应符合有关标准。
A. 地界标
B. 管界桩
C. 地界桩
下面（）不属于CNC装置的基本功能。
A. 主轴功能
B. 进给功能
C. 准备功能
D. 图形显示功能
Which method would you use to undo the changes made by a particular transaction without affecting the changes made by other transactions？（）
A. point-in-time recovery
B. execute the ROLLBACK command with transaction number
C. flashback the database to before the transaction was committed
D. determine all the necessary undo SQL statements from FLASHBACK_TRANSACTION_QUERY and use them for recovery
Precondition字段是在哪条消息中携带的（）。
A. INVITE Request
B. 100Trying
C. 183response
D. 200OK
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