The selected IPv4 plan is correct because the design must maximize the number of subnets while still meeting the host requirements for each location. With VLSM, the largest subnet must be allocated first. A segment requiring 500 hosts needs at least 9 host bits, because 2^9 provides 512 addresses and 510 usable host addresses, so a /23 is required. A segment requiring 100 hosts needs 7 host bits, giving 126 usable addresses, so a /25 is sufficient. A segment requiring 25 hosts needs 5 host bits, giving 30 usable addresses, so a /27 is sufficient. Any plan that uses larger prefixes than necessary wastes addresses and reduces the number of available subnets inside 172.16.0.0/16. Any plan using smaller subnets would fail the host requirement. The correct option is the one that uses the smallest valid subnet size for each requirement while keeping the addressing blocks aligned. Reference topics: IPv4 VLSM, CIDR, subnet sizing, usable host calculation, hierarchical addressing plans.