We can’t confirm answer B is totally correct but all other answers are wrong so B is the best choice.
+ We only have 1 LAN interface on Main_Campus router with 4 subinterfaces -> answer A is not correct (although it is a bit unclear).
+ The “protocol” column of interface Serial0/1 is up so its Layer 2 is operating correctly -> answer C is not correct.
+ This router has only 1 FastEthernet interface -> answer D is not correct.
+ The “status” column of Fa0/0 is currently “up” so it is operating -> answer E is not correct.
Fa0/1 of Switch11 is configured as an access link of VLAN1 so only frames in VLAN1 can communicate through the two switches. But from the output above we see there is no interface belongs to VLAN1 on Switch12 -> no hosts can communicate between the two switches.