Comprehensive and Detailed Explanation:
When anew VLAN is created, it typically exists on a different subnet. IfDHCP servers are on a different VLAN, the networkneeds an IP helper addressto forward DHCP requests correctly. Without it, clients in the new VLANwon't receive an IP address.
Breakdown of Options:
* A. Scope size- Increasing the DHCP scope would not resolve the issue if requestsaren't reaching the server.
* B. Address reservations- Reservations only assign specific addresses to devices; they do not fix DHCP communication issues.
* C. Lease time- Changing the lease timedoes not impact DHCP functionality across VLANs.
* D. IP helper-Correct answer.This forwardsDHCP requestsacross VLANs to the DHCP server.