What would accomplish this goal?

Refer to the Exhibit

You work for the regional Internet service provider shown in the exhibit You have a partial BGP
table and are receiving a 10 100/16 route from your upstream ISP You have been asked to
configure a default route that can be sent to your downstream customer This route should forward
customer traffic toward your upstream Tier 11SP as long as the 10.100/16 route is present.
What would accomplish this goal?

A.
Create and announce an aggregate default route

B.
Create and announce a static default route with a next-hop of discard

C.
Create and announce a static default route with a next-hop of reject

D.
Create and announce a generated default route

E.
Create an advertise-map with exist-map

Explanation:
Reference:
http://www.juniper.fr/techpubs/en_US/junose10.0/information-products/topic-collections/swconfig-bgp-mpls/advertising-a-default-route-only-when-another-route-is-present.html