Huawei Exam H31-161 Topic 2 Question 18 Discussion

As shown in the figure, RTA, RTB, and RTC use the OSPF protocol. The default cost value is used for links, and unicast routes converge on the entire network. The Loopback 0 interface is set to configure RTC as the RP or BSR. The SPT switching threshold uses the default value on RTB. The receiver joins the multicast group 225.1.1.1. The multicast source sends multicast data to the destination address 225.1.1.1. Which interface is the inbound interface in the (10.1.1.1, 225.1.1.1) entry on RTB?