Which technology relies on STP as a failsafe mechanism?

Which technology relies on STP as a failsafe mechanism?
A . FabricPath
B . MPLS
C . VXLAN
D . vPC

Answer: D

Explanation:

vPC technology allows to build a loop free topology by levering port-channel from access device to vPC domain. A port-channel is seen as a logical link from STP standpoint so vPC domain with vPC-attached access device globally form a star topology at L2 (there is no STP blocked ports in this type of topology). For that case, STP is used as a fail-safe mechanism to protect any network loop caused by human error (like plugging a loopback cable across the 2 vPC peer device).

Reference: https://www.cisco.com/c/dam/en/us/td/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf