You want to mitigate failures that are caused by STP loops that occur before UDLD detects the failure or that are caused by a device that is no longer sending BPDUs. Which mechanism do you use along…

Root Guard prevents inferior BPDUs from causing a port's switch to accept a new root bridge, which addresses root placement stability rather than loop prevention from missing BPDUs.

BPDU Guard is designed for PortFast-enabled access ports and disables a port if any BPDU is received, which is the opposite behavior needed and does not prevent loops from missing BPDUs.

Loop Guard prevents a non-designated port from transitioning to the forwarding state if it stops receiving BPDUs, protecting against loops that form when a device silently stops sending BPDUs. While UDLD addresses physical unidirectional link failures, Loop Guard covers the logical scenario where BPDUs simply disappear, such as a software failure on the upstream switch. Together they provide complementary protection across both physical and logical failure modes.

BPDU Filtering suppresses BPDU transmission and reception on a port, effectively disabling STP on that segment and increasing loop risk rather than mitigating it.