在子网的分割过程中（assume older version UNIX workstation are in ues） 这句话起了什么作用？
Such as:
what is the maxumum number of subnets that can be assigned to netowrks when using the address 172.16.0.0 with a subnet mask of 255.255.240.0?(assume older version UNIX workstations in in use)
A.16
B.32.
C.30
D.14
