Which of the following best describes how Sirius radio receivers operate?

Sirius radio receivers are designed to operate by receiving signals from orbiting satellites, which enables them to provide a wide range of audio programming over large geographic areas. This satellite-based system allows for continuous coverage, as the signals can reach receivers regardless of the user's location, including remote areas where terrestrial signals might not be accessible.

The design of Sirius radio's infrastructure relies on satellites that transmit signals directly to receivers, offering a vast array of channels without the limitations typically imposed by ground-based broadcasting methods. This satellite-to-receiver communication is supported by a network of repeaters that enhance signal quality and coverage in urban environments, where buildings might obstruct satellite signals.

The other options suggest methods of signal reception that do not align with how Sirius radio operates, emphasizing reliance on terrestrial or ground-based systems, limited geographical service, or a combination of those methods, which would contradict the satellite-dependent nature of Sirius radio technology. The effectiveness and adaptability of satellite communication in various environments make option C the most accurate description of how Sirius radio receivers function.