They ask about convergence between 3 devices at Layer 3 , UDLD is for switched networks not for layer 3 , also Copper media is not susceptible to unidirectional issues since they use FLP to monitor the link .and the main logic here is the UDLD will not help you if there is a 3 switches and one of the links go down to converge faster answer should be with BFD included . Another clue here is we talk about links that are in the same rack so here cost effective will be to use Copper media to connect this switches , despide that Copper will be slower if we rely on debunce timer . so here answer should be A .
