The correct answer is D: Increase the scope to 10.8.100.50 – 10.8.100.175. According to the CompTIA Network+ N10-009 objectives, proper DHCP scope configuration is essential to ensure all hosts can obtain valid IP addresses and communicate beyond their local segment.

In this scenario, the DHCP scope is configured for 10.8.100.50 through 10.8.100.150, while a reservation range exists from 10.8.100.151 through 10.8.100.175. The network scan shows that IP addresses up to 10.8.100.175 are already in use. This indicates that some devices are either statically assigned addresses outside the active scope or are failing to receive valid DHCP leases, causing the new laptops to communicate only with each other—often a sign of APIPA or improper addressing.

To ensure full connectivity, the DHCP scope must be expanded to include the entire range of addresses that are actively in use, including the reserved addresses. Option D correctly extends the scope to 10.8.100.175 without overlapping lower addresses that may be statically assigned or intentionally excluded.

The Network+ objectives emphasize avoiding address conflicts and ensuring DHCP scopes align with real-world network usage. Expanding the scope to include all valid addresses ensures that all laptops can obtain proper IP configuration, default gateway information, and full network connectivity.