What is the reason the route is not advertised?

Refer to the exhibit.

R2 is a route reflector, and R1 and R3 are route reflector clients. The route reflector learns the route to 172.16.25.0/24 from R1, but it does not advertise to R3.

What is the reason the route is not advertised?
A . R2 does not have a route to the next hop, so R2 does not advertise the prefix to other clients.
B . Route reflector setup requires full IBGP mesh between the routers.
C . In route reflector setup, only classful prefixes are advertised to other clients.
D . In route reflector setups, prefixes are not advertised from one client to another.

Answer: A

Explanation:

With route reflector (RR), we only need to establish a BGP session from the RR to each internal peer->Answer A is not correct.

We can advertise both classful and classless prefix to other clients, provided that the prefix satisfies the RR forwarding rules->Answer Band answer Care not correct.

Therefore only answer Dis left. Maybe we are missing an IGP in our topology so R2 did not know how to reach the next hop reported by the prefix.