The correct answer is option 'C': a receiver.

Explanation:
A TV set is a device that is used to receive television signals and display them as audio and visual content on a screen. Let's break down the explanation further:

1. TV Set: A TV set, also known as a television or television receiver, is an electronic device used for watching television programs. It consists of a display screen, built-in speakers or audio output, and various controls for adjusting settings such as volume, channel selection, and picture quality.

2. Receiver: In the context of television, a receiver is a device that receives television signals and converts them into audio and visual content that can be displayed on a TV screen. The TV set acts as a receiver by accepting incoming signals and decoding them to produce the desired television program or content.

3. Television Signals: Television signals are transmitted through electromagnetic waves. These signals are generated by TV stations or broadcasters and contain audio and video information that represents the television program being transmitted. The TV set receives these signals and processes them to display the program on the screen.

4. Channel Selection: A TV set allows users to select different channels to access various television programs. Channels are specific frequencies or frequency ranges used for broadcasting different programs. The TV set receives the selected channel's signal and displays the corresponding program on the screen.

5. Additional Functionality: Modern TV sets often have additional features and capabilities, such as the ability to connect to the internet, access streaming services, or display content from external devices. However, the core function of a TV set is to receive television signals and display them as audio and visual content.

In summary, a TV set is primarily a receiver that accepts television signals and converts them into audio and visual content that can be displayed on a screen. It enables users to select channels and watch various television programs.