What is a constraint of Cisco MPLS TE tunnel configurations?
A. QoS-aware tunneling is not supported.
B. Tunnels cannot be configured over IP unnumbered links.
C. With ISIS as an IGP, only older-style metrics are used.
D. Tunnels cannot span multiple OSPF areas.
Think the correct answer is D
https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k-r6-2/mpls/configuration/guide/b-mpls-cg-asr9000-62x/b-mpls-cg60x-asr9k_chapter_01000.html