Refer to the exhibit.

These three routers are currently configured for BGP. They do not apply any routing policy in terms of BGP on
routes or attributes advertised to an received from peers. How can the network administrator for Router 1 cause
Router 1 to advertise 192.0.2.0/24 to Router 2 and Router 3?

A.
Enable BGP routing on RAGG1

B.
Add a null route to 192.0.2.0/24

C.
Apply route policy 1 as an inbound policy for both peers

D.
Apply route policy 1 as an outbound policy for both peers

Explanation:
You can associate a route policy to a BGP peer. Route policies use route maps to control or modify the routes
that BGP recognizes. You can configure a route policy for inbound or outbound route updates.
Incorrect:
Not B: Null 0 routing is used to prevent routing loops in some conditions as if any packet is destinated for some
specific route in that subnet which is not available for an example is down due to any reason instead of going
through the default route and packet reaching somewhere else packet destined for that specific route within
that subnet must be dropped.
So basically NULL 0 creates a block hole where if packets are matched is dropped.
Configuring Advanced BGP
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/unicast/configuration/guide/l3_cli_nxos/
l3_advbgp.html