Refer to the exhibit. Why is a route leaking mechanism needed in this large, unified MPLS network with end-to-end BGP labeled prefixes and IS-IS multilevel areas as the IGP?

PE management access via Telnet or SNMP does not require IS-IS route leaking; management reachability is handled through out-of-band networks or default routes.

Route leaking in IS-IS flows from Level 1 areas up into the Level 2 backbone, not from the backbone down to Level 1 areas, which is the reverse of what this option states.

LSPs are built by the label distribution protocol (LDP or RSVP-TE) based on IGP reachability; route leaking is a prerequisite for that IGP reachability, not a direct mechanism for building LSPs.

In IS-IS, Level 1 routers only have visibility within their own area and do not advertise prefixes into the Level 2 backbone by default. PE loopbacks residing in L1 areas must be explicitly leaked into the L2 backbone so that all PEs can resolve BGP next-hops and establish end-to-end label-switched paths across the unified MPLS network.