Refer to the exhibit.

What is the most likely reason for the disparity between the actual network numbers at the brances and the routes in the routing table on Gateway_Router?

A.
Gateway_Router is configured to receive only RIPvl updates.

B.
Gateway_Router is configured to only receive RIPv2 updates.

C.
Branch_Router2 is configured to send both RIPvl and RIPv2 updates.

D.
Branch_Router1 is configured to only send RIPvl updates.

Explanation:
The default version of RIP is version 1, which doesn’t supports multicast updates, classless networks, and authentication. It appears that Routerl is configured with RIP v1 so it’s sending only v1 packets, which means only the classful network of 208.149.23.0/24 is being advertised. However, it appears that Router2 is indeed using RIPv2 as both the 121 networks are being advertised from that router.
If you wish to enable to RIP version 2 on router use following command:
Router(Config)#router rip Router(Config-router)#version 2