What subnet mask would accommodate this network?

Refer to the exhibit.

The enterprise has decided to use the network address 172.16.0.0. The network administrator needs to design a classful addressing scheme to accommodate the three subnets, with 30, 40, and 50 hosts, as shown.

What subnet mask would accommodate this network?
A . 255.255.255.192
B . 255.255.255.224
C . 255.255.255.240
D . 255.255.255.248
E . 255.255.255.252

Answer: A

Explanation:

Subnet mask A i.e. 255.255.255.192 with CIDR of /26 which means 64 hosts per subnet which are sufficient to accommodate even the largest subnet of 50 hosts.