A user is unable to print to the network printer. A print job appears in their print queue and cannotbe deleted. The user has the correct permissions to modify and delete print jobs. All other users are able to print to the network printer. Which of the following procedures should the technician try FIRST?（）

A、Cycle the power on the network printer.

B、Verify the network cable is connected to the printer.

C、Reinstall the printer driver.

D、Restart the print spooler service.

如图所示，对该正六边形进行打断操作，系统要求指定第二打断点，这时输入了@，然后回车结束，操作后的图形周长为？（）

A、0

B、600

C、599

D、在0~600中随机分配

在switch（expression）语句中，expression的数据类型不能是（）。

A、double

B、char

C、byte

D、short

某寄存器中的值有时是数值，有时又是地址，这只有计算机的（）才能识别它。

A、译码器

B、判断程序

C、指令

D、时序信号

You execute the following Recovery Manager （RMAN） commands in he following order：   BACKUP VALIDATE DATABAE RECOVER CORRUPTION LIST；   Which two tasks are performed by these commands？（）  

 Repair the corrupted blocks. If any. In the backup created

 Populate VSCOPV_CORRUPTION with names of files that have corrupted blocks

 Back up the database after checking whether array of the files have corrupted blocks

 Discover any corrupt blocks that are viewable with the VSDATABASE_BI-OCK_CORBUPTION view

 Repair all corrupted blocks that have been logged in the VSDATABASE_BLOCK_ CORRUPTION

Which command will create a group called ’delivery’ and set the administrators to ’john’ and ’mary’？（）  

A、mkgroup -A=john，mary delivery

B、groupadd -A=john，mary delivery

C、mkgroup adms=john，mary delivery

D、groupadd adms=john，mary delivery