Explanation
Aggregate routes are used for advertising summarized network prefixes12. They help minimize the number of routing tables in an IP network by consolidating selected multiple routes into a single route advertisement1. This approach is in contrast to non-aggregation routing, in which every routing table contains a unique entry for each route1.
Therefore, option D is correct. Options A, B, and C are not correct because:
Aggregate routes can be used with both static routing and dynamic routing protocols1.
Aggregate routes are not automatically generated for all of the subnets in a routing table. They need to be manually configured1.
Aggregate routes are not always preferred over more specific routes. The route selection process in Junos OS considers several factors, including route preference and metric, before determining the active route1.