Explanation/Reference:
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.
Reference: 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