By using a subnet mask of 255.255.255.128, you can split that network into two halves, with the
second half containing the host addresses from:

A.
129 to .254

B.
128 to .254

C.
129 to .255

D.
128 to .255

Explanation:
By using a subnet mask of 255.255.255.128, you can split that network into two halves, the first
half containing the host addresses .1 through .126, the second half containing the host addresses
.129 through .254. Note that on a true class “C” network, you can’t use the top subnet, since the
bit in the subnet portion (one bit on a class “C”) would be one (refer to ground rule “D”.)