Which type of cable is designated to carry video signal only?

The correct choice for a cable designated to carry video signal only is the BNC cable. BNC cables are primarily used in professional video settings to transmit video signals, providing a reliable connection that minimizes interference. They are commonly utilized in CCTV systems and broadcast television because they carry composite video, which is a singular unbroken video signal.

While RCA cables can also carry video signals, they are typically used for both audio and video, and in many configurations, they handle multiple signals (e.g., stereo audio channels and composite video). The S-Video cable is designed to carry video signals but is intended for higher-quality video than standard composite signals, often splitting the brightness and color components for better fidelity, rather than strictly carrying video itself. The 1/4" phone plug is primarily used for audio signals, particularly in instruments and microphones, rather than video, making BNC the clear choice for a cable dedicated solely to video transmission.