Which statement about OSPF incremental SPF is true?

iSPF has no domain-wide enablement requirement because it is a local algorithmic optimization, not a protocol extension that peers must support.

Area-wide enablement is not required for the same reason - iSPF affects only the local router's SPF computation, not how LSAs are flooded or processed by neighbors.

iSPF does not use Opaque LSAs because it is never advertised to or negotiated with peers - it is invisible to the rest of the OSPF domain.

iSPF is purely a local computation optimization on the router that processes its own link-state database. Because it does not change any OSPF protocol messages or LSA formats, neighboring routers need no knowledge of it - a router running iSPF interoperates transparently with routers that run full SPF.

OSPF adjacency formation uses Hello packets and the DBD/LSR/LSU/LSAck exchange; iSPF is not part of this process and is never negotiated.