使用FTP传送任何类型的文件，在进行文件传送时，FIT客户机和服务器之间要建立两个连接：控制连接和——。
A. 网络连接
B. UDP连接
C. 数据连接
D. IP连接
Umbrellas were firstly used to keep people from ______.
A. sun
B. rain
C. animals
As regards walking to school, modern parents seem much concerned about______.
A. the sudden changes in the route
B. their children's physical conditions
C. their children's safety on the way
D. the distance their kids have to take
以下哪个命令是配置1P地址池的子网地址和子网掩码的？——
A. ip dhcp excluded—address
B. network address mask
C. default—router address
D. ip dhcp pool＜name＞
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