Refer to the exhibit. Router E learned about the PIM RP （designated as 7.7.7.7） from four different sources. Routers A and D advertised the 7.0.0.0 network via EIGRP. Routers B and C advertised the 7.0.0.0 network via OSPF. Considering that all four Ethernet interfaces on router E could potentially lead back to the PIM-RP， when router E receives the first multicast packet down the shared tree， which incoming interface will be used to successfully pass the RPF check？（）