A.表单
B.表格
C.链接
D.框架集

A.事务
B.更新
C.插入
D.以上都不是

A.无区别
B.count是聚合函数，count（*）不是聚合函数
C.count统计空格而COUNT（×）不统计
D.count（*）统计NULL值，而COUNT不统计

A.DECLARE
B.SET
C.USE
D.GET

A.ity=null
B.city='null'
C.city is null
D.city is 'null'

A.service named stop
B./etc/rc.d/init.d named stop
C.kill -9 named
D.kill -9 2567

A.c
B.b
C.l
D.d

A.bg
B.renice
C.jobs
D.who

A.-l
B.-a
C.-m
D.-s

A.Sam
B.users
C.root
D.sys

A.tar cvf
B.tar xvf
C.tar zcvf
D.tar zxvf