Company XYZ wants to redesign the Layer 2 part of their network to use all...

A (TRILL - Transparent Interconnection of Lots of Links):TRILL enables multipathing at Layer 2, eliminating classic STP blocking, allowing all uplinks to be active simultaneously, and uses IS-IS based control plane for conversational MAC learning.

Other options explained:

B: LISP operates at Layer 3 for endpoint mobility, not Layer 2 multipathing.

C: MSTP still blocks some links under normal operation.

D: Switch stacking merges multiple physical switches into one logical switch but does not provide true multipathing across independent switches.