单选题What is the purpose of a network mask?（）A It is used in conjunction with the wildcard mask to determine the number of hosts on a networkB It is used to define which parts of the IP address are allocated to host addresses and network prefixesC It is use
题目
单选题
What is the purpose of a network mask?（）
A
It is used in conjunction with the wildcard mask to determine the number of hosts on a network
B
It is used to define which parts of the IP address are allocated to host addresses and network prefixes
C
It is used to hide subnets from external networks by masking the subnets with NAT
D
It is used to differentiate a network as a classful network or a classless network