Address Resolution Protocol $($ARP$)$ is used by computers to resolve a Network Layer or IP address, into a Data Link Layer or physical address. Network Discovery Protocol $($NDP$)$ is very similar to ARP with what major difference?

a$.$ NDP runs over ICMPv$6$ and uses multicast packets sent by one IPv$6$ host to request the physical address of another IPv$6$ host.

b$.$ NDP runs over ICMP and uses multicast packets sent by one IPv$4$ host to request the physical address of another IPv$4$ host.

c$.$ NDP runs over ICMPv$6$ and uses broadcast packets sent by one IPv$6$ host to request the physical address of another IPv$6$ host.

d$.$ NDP runs over ICMP and uses broadcast packets sent by one IPv$4$ host to request the physical address of another IPv$4$ host.