When an operating OSPF router receives an LSA and the LSA does not exist in its link state database, how does the router handle this LSA?

When an operating OSPF router receives an LSA and the LSA does not exist in its link state database, how does the router handle this LSA?
A . The router will silently discard this LSA without returning any messages.
B . This LSA will be immediately flooded to other OSPF neighbors.
C . The LSA is installed in its own link state database, and then this LSA is acknowledged by multicast.
D . Check the age of the LSA to see if it expires.

Answer: D