While paralleling two AC generators using synchronizing lamps only, both lamps will go dark when the generators are （）.
A. running at the same speed
B. grounded
C. of the same polarity
D. in phase
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当蒸汽中含有空气时，空气附在冷却面上影响蒸汽通过，使热阻（），水蒸汽凝结换热显著（）。
明朝早期都城南京应天府城墙不仅是世界上规模最大的古城，也是目前我国仅存的古都都城。（）
A. 正确
B. 错误
In which scenario， will you issue the following command？（） RMAN> REPORT NEED BACKUP DAYS 7；
A. to configure RMAN to maintain backup information in the RMAN repository for seven days
B. to configure RMAN to maintain backup information in the control file for at least seven days
C. to display the list of files that have not been backed up for the last seven days
D. to display the list of files that must be backed up within seven day
郭声琨部长在公安现役部队党的建设工作会议上指出，加强公安现役部队党的建设，（）是关键。
A. 正、副书记
B. 领导干部和普通党员
C. 领导班子和领导干部
D. 广大党员
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