You are planning the network for a branch office.

The branch office will contain 100 IPv4 hosts.

You need to recommend a subnet mask for the branch office. The subnet mask must minimize the number of unused IP addresses.

Which subnet mask should you use?

A.
255.255.255.0

B.
255.255.255.128

C.
255.255.0.0

D.
255.255.128.0

Explanation:
http://www.pantz.org/software/tcpip/subnetchart.html