Which step can be taken to ensure that only FortiAP devices receive IP addresses from a DHCP server on FortiGate?

Which step can be taken to ensure that only FortiAP devices receive IP addresses from a DHCP server on FortiGate?
A . Change the interface addressing mode to FortiAP devices.
B . Create a reservation list in the DHCP server settings.
C . Configure a VCI string value of FortiAP in the DHCP server settings.
D . Use DHCP option 138 to assign IPs to FortiAP devices.

Answer: C