Final answer:
The C. CSU/DSU (Channel Service Unit/Data Service Unit) is the device that terminates a dedicated leased line circuit, connecting the router to the telecommunications network for secure data transmission.
Step-by-step explanation:
The device that terminates a dedicated leased line circuit is c) CSU/DSU (Channel Service Unit/Data Service Unit). These devices are essential for connecting a leased line to a router or other network devices. The CSU/DSU converts digital data frames from the communications technology used on a local area network (LAN) into frames appropriate for the wide area network (WAN) and vice versa. They are the physical devices that connect the router to the point-to-point leased line and ensure that the digital signals are transmitted securely and accurately over the telecommunications network.
The device that terminates a dedicated leased line circuit is called a CSU/DSU (Channel Service Unit/Data Service Unit).
A CSU/DSU is a device that connects a router or switch to a dedicated leased line. It is used to convert digital signals between the router/switch and the leased line.
For example, if a company has a dedicated leased line for their internet connection, the CSU/DSU would be connected to the router, and then the leased line would be connected to the CSU/DSU. This allows the router to communicate with the outside network through the leased line.