In order to configure two routers as anycast RPs， which of these requirements， at a minimum， must be satisfied？（）
- AMulticast Source Discovery Protocol mesh-groups must be configured between the two anycast RPs.
- BThe RPs must be within the same IGP domain.
- CMulticast Source Discovery Protocol must be configured between the two anycast RPs.
- DThe two anycast RPs must be IBGP peers.