以下关于%ROWTYPE的作用说法正确的是（）。

A、使用%ROWTYPE来定义一个表示表中一行记录的变量

B、使用%ROWTYPE的变量不能实现将一行记录的部分字段赋值

C、使用%ROWTYPE将一个变量的数据类型与一张表中记录的各个列的数据类型保持一致

For security reasons， an administrator is asked to modify the system to prevent someone from leaving a terminal logged in. To enable a five minute timeout for all users， what would need to be done to accomplish this task？（）

A、Add the following line to /etc/environment：  TMOUT=300

B、Add the following lines to /.profile  TMOUT=5  export TMOUT

C、Execute the following command：  chuser -u ALL -a TIMEOUT=5M

D、Execute the following command：  chsec -u ALL -a TIMEOUT=600

以下选项中不合法的标识符是（　　）。

A、print

B、FOR

C、&a

D、_00

A remote user is trying to telnet to the production server. The session is getting a timeout error. Which command should the user issue to verify the network connection？（）

A、iptrace

B、nslookup

C、netstat

D、traceroute

What is the role of route preference?（）

A、It is used as a tie breaker when the same prefix is available through multiple sources

B、It is used to determine which routes to accept into the routing table

C、It is used to select the best route between multiple equal-cost paths

D、It is used to select which routing table to use for forwarding

Given the following scripts， what output would be generated？（）

A、 The sky is red.

B、 The sky is blue.

C、 The sky is green.

D、 The sky is yellow.