In an OSPF environment, what must a router receive after it sends out an update?

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Reliable Flooding and Acknowledgments):

“Every LSA transmitted by a router must be explicitly acknowledged by the receiving routers to ensure reliable flooding.”

LSAs use explicit acknowledgment via OSPF LSAck packets.

Without acknowledgment, retransmission occurs.

Thus, correct answer is A.

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