What new module is pre-installed in the Cisco 3900 Series ISRs?

The correct answer is Service Performance Engines. The Cisco 3900 Series Integrated Services Routers (ISRs) are designed to offer enhanced performance, scalability, and advanced features suitable for a variety of enterprise environments. Service Performance Engines refer to dedicated hardware components that significantly boost the processing capability of the router, especially for demanding services like voice and video. By integrating these engines into the ISRs, Cisco ensures that the routers can handle higher levels of service and traffic without degrading performance, making them ideal for organizations that require robust and reliable network services.

The other options do not accurately reflect the specific enhancements that the Cisco 3900 Series ISRs provide. High-Speed WAN Interface Card, Enhanced Ethernet Module, and Modular Router Processor are features associated with various router capabilities, but they are not unique to the 3900 Series or indicative of the latest pre-installed advancements aimed at improving overall service performance at the hardware level. Thus, focusing on the Service Performance Engines highlights the distinctive capabilities of the 3900 Series in managing increased demands and service quality in modern networking scenarios.