'Different IP networks' denotes Layer-3. As such, these need to be able to route between the sites and to route you need a gateway (default or static).
Since each datacenter will use different IP networks, L3 is required, so answer A is ruled out.As per B, you can script/select different port groups.So C and D look like the correct answers (as per "Use the vMotion TCP/IP stack to isolate traffic for vMotion and to assign a dedicated default gateway, routing table, and DNS configuration for this traffic - https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.vcenterhost.doc/GUID-5211FD4B-256B-4D9F-B5A2-F697A814BF64.html#GUID-5211FD4B-256B-4D9F-B5A2-F697A814BF64)As per Oliver's link, L2 is a requirement for VM network and L3 is supported for vMotion