Which two Cisco platforms can be used together to easily model WAN services and examine the impact of changes?

The correct choice is the combination of platforms that allows for effective modeling of WAN services and analysis of potential changes. The use of VTS, or Virtual Transport Switching, in conjunction with another platform facilitates comprehensive digital twin capabilities which enhance the ability to simulate and understand the behavior of WAN services.

VTS provides a visual representation of network services and enables administrators to test various scenarios in a safe environment. This ability to model changes allows for better planning and decision-making about WAN architecture and service delivery. When combined with another Cisco platform, it can effectively simulate how alterations in configurations, capacity, or other parameters might affect overall service performance and reliability.

ACI (Application Centric Infrastructure) and NSO (Network Services Orchestrator) do provide valuable capabilities in network management and orchestration but are not specifically designed for detailed modeling of WAN services in the same way that VTS does when paired with another appropriate platform. WAE (Wide Area Application Services), while it deals with WAN optimization, does not focus primarily on the modeling aspect, making it less suitable for the purpose of the question.