Refer to the exhibit. There is reachability among all routers. An MPLS TE auto-tunnel mesh is deployed in all routers. A full mesh auto-tunnel is created successfully among RTB, RTC, RTE, RTD, and RTF routers. RTA router is able to build an automatic MPLS TE tunnel that has only RTB and RTC routers as destinations. Why is the RTA router unable to build an automatic MPLS TE tunnel that has RTE, RTD, or RTF routers as destinations? 

Answer options:

A. Tunnel affinity is not supported for full mesh auto-tunnels.
B. Auto-tunnel mesh groups do not support interarea tunnels.
C. An explicit path that identifies the L1L2 routers among RTC, RTE, RTP, and RTF is required.
D. IS-IS does not support auto-tunnel mesh groups, only OSPF does, via opaque LSA.

B

Reference: https://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/gsmeshgr.html