Refer to the exhibit. Each router must be configured with the last usable IP address in the subnet. Which configuration fulfills this requirement?

With a 255.255.255.192 mask, 10.88.31.127 is the broadcast address for the 10.88.31.64/26 subnet and cannot be assigned to an interface.

While 10.88.31.126 is the last usable IP in a 10.88.31.112/28 subnet, this option is incorrect if the network design (from the unprovided exhibit) specifically dictates a /26 subnet or a different subnet range.

With a 255.255.255.240 mask, 10.88.31.127 is the broadcast address for the 10.88.31.112/28 subnet and cannot be assigned to an interface.

A subnet mask of 255.255.255.192 corresponds to a /26 prefix, which divides a network into blocks of 64 addresses. For the network segment containing 10.88.31.126, the specific subnet would be 10.88.31.64, with a broadcast address of 10.88.31.127. Therefore, 10.88.31.126 is indeed the last usable host IP address in the 10.88.31.64/26 subnet, fulfilling the requirement.