Which of the following describes the purpose of a transmitter in radio communication?

The purpose of a transmitter in radio communication is fundamentally to convert electrical energy into radio waves, making option C the correct choice. Transmitters work by taking modulated electrical signals—representing audio, video, or other data—and converting them into electromagnetic waves that can propagate through the air. This transformation is crucial for enabling communication over distances, allowing information to be sent from one location to another wirelessly.

The other options relate to different functions within the communication process but do not define the role of a transmitter. For instance, receivers are responsible for receiving and decoding signals (as mentioned in option A), maintaining signal levels pertains more to amplifiers or filters rather than transmitters (related to option B), and filtering background noise is typically a function of receivers or signal processing equipment rather than transmitters (as indicated in option D). Thus, option C accurately captures the essential function of a transmitter within radio communication systems.