A ____ is a device closest to end users, used to access the network and switch data frames. A. Router B. Gateway C. Switch D. Terminal device.

To solve the question, let's analyze the options provided:

1. Routers: These devices route data between different networks. While they can connect end users, they primarily operate at a different layer in networking.

2. Gateways: These are used to connect networks that use different protocols, functioning as a "gate" between them. They are not specifically designed for end users.

3. Switches: Switches are devices used within a single network to connect devices (computers, printers, etc.) and allow them to communicate. They operate at the data link layer and are indeed closest to end users.

4. Terminal devices: This term generally refers to end-user devices that can be connected to a network, like computers or phones, but they don’t switch data frames.

Given the definitions, the answer is clear.

Final Answer

C. Switch is the device closest to end users, used to access the network and switch data frames.