An engineer must allow routes learned from one L3Out to be advertised out another L3Out. The engineer does not have an explicit list of all the routes that must be advertised out, however, they know that they are all part of the 10.16.0.0/16 CIDR block. Which attributes must be selected under Ext-EPG to allow the necessary routes to be advertised out?

When allowing routes learned from one L3Out to be advertised out another L3Out, the Export Route Control Subnet should be enabled, and Aggregate Export should also be enabled. This configuration allows the necessary routes within the specified CIDR block to be aggregated and advertised out, facilitating efficient route advertisement without the need for an explicit list of all routes.
Reference: Implementing Cisco Application Centric Infrastructure Official Cert Guide