在hz表里添加类型为nvchar字节为8的tea_name字段命令是以下哪个选项？（)

A、alter database hz drop column tea_name

B、alter table hz drop column tea_name

C、alter table tea_name drop column hz

D、alter database tea_name drop column hz

A、insert into hz (tea_name) values (leon)

B、insert into tea_name (hz) values ('leon')

C、insert hz into (tea_name) values ('leon')

D、insert hz into (tea_name) value ('leon')

A、delete from hz where tea_ID>3

B、delete where hz from tea_ID>3

C、drop from hz where tea_ID>3

D、drop where hz from tea_ID>3

A、update hz set tea_name='leon' where tea_name='lisa'

B、update hz set tea_name='lisa' where tea_name='leon'

C、insert into tea_name (hz) values ('lisa')

D、insert into tea_name (hz) values ('leon')

A.3

B.4

C.5

D.8

A.报头长度为20~60字节，其中固定部分为20字节

B.端口号字段依次表示源端口号与目的端口号

C.报头长度总是4的倍数个字节

D.TCP校验和伪首部中IP分组头的协议字段为17

A.icmp

B.icmp=8

C.icmp[0]=8

D.icmp[0]=0

A.8

B.20

C.30

D.40

A.图表选项

B.图表类型

C.添加数据

D.源数据