当输气站计量系统出现故障时，SCADA系统中将会出现报警，其中中控SCADA系统中流量计画面显示的报警有哪三种状态报警？

A list of files that require a backup within 3 days
B. A list of files requiring more than 3 days of archivelogs to apply
C. A list of files that RMAN recommends be backed up only once in every three days, based on low volatility
D. A list of files for which a backup as already been performed in the last three days and which is required to be backed up again based on the high number of transactions performed on them

A. angle that the propeller makes with a free stream of water
B. angle that the propeller makes with the surface of the water
C. number of feet per revolution the propeller is designed to advance in still water without slip
D. positive pressure resulting from the difference of the forces on both sides of the moving propeller in still water without sli

A. 全天一次
B. 上午一次
C. 下午一次
D. 上、下午各一次，间隔6小时
E. 上、中、下午各一次，共三次