Which device acts like a border router to connect corporate sites to wired access lines?

The most appropriate choice for a device that acts like a border router to connect corporate sites to wired access lines is Customer Premises Equipment (CPE). CPE encompasses a variety of devices that facilitate communication at the customer's location, including routers, modems, and other networking hardware. It typically connects end-users or corporate sites to telecommunication networks, effectively serving as a demarcation point between the customer’s private network and the service provider's infrastructure.

In particular, CPE can manage traffic and may include routing functionalities, which means it helps in directing data packets between different network segments or between a corporate network and the internet. This aspect of managing connections and routing is crucial for maintaining efficient communication for corporate sites.

Considering other options: while a modem converts signals for data transmission, it does not primarily serve as a border router. A router does facilitate network routing and connecting different networks but is generally considered part of the CPE category. An access point primarily extends wireless connectivity within a network but does not connect corporate sites to wired access lines. Thus, CPE is the most complete choice as it encapsulates the role of connecting and routing at the customer's premises effectively.