Refer to the exhibit.

EIGRP has been configured on all routers in the network. What additional configuration statement
should be included on router R4 to advertise a default route to its neighbors?

A.
R4(config)# ip default-network 10.0.0.0

B.
R4(config)# ip route 0.0.0.0 0.0.0.0 10.1.1.1

C.
R4(config)# ip route 10.0.0.0 255.0.0.0 10.1.1.1

D.
R4(config-router)# default-information originate

Explanation:
Unlike the ip default-gateway command, you can use ip default-network when ip routing is enabled
on the Cisco router. When you configure ip default-network the router considers routes to that
network for installation as the gateway of last resort on the router.
For every network configured with ip default-network, if a router has a route to that network, that
route is flagged as a candidate default route.
Gateways of last resort selected using the ip default-network command are propagated differently
depending on which routing protocol is propagating the default route. For IGRP and EIGRP to
propagate the route, the network specified by the ip default-network command must be known to
IGRP or EIGRP. This means the network must be an IGRP- or EIGRP-derived network in the
routing table, or the static route used to generate the route to the network must be redistributed
into IGRP or EIGRP, or advertised into these protocols using the network command. In this case,
the 10.0.0.0 network is indeed being advertised via EIGRP.

Reference:
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.shtml#ipnetwork