How will it appear in the METAR when no clouds below 12,000 feet are reported at an automated station?

In METAR reports, when there are no clouds reported below 12,000 feet at an automated weather station, it is indicated as "CLR," which stands for "clear." This term is used to signify that the sky is clear of any significant cloud cover that might affect visibility or weather conditions at that particular altitude.

Using "CLR" is standard practice, particularly in automated reports, to provide a concise way to communicate that the observer did not detect any clouds in the lower atmosphere, which is crucial for pilots and meteorologists when evaluating current weather conditions.

The other choices do not accurately represent the METAR standard for reporting clear skies. "SKC" also means "sky clear," but it is traditionally used instead of "CLR" in manual reports. "OCNLY" refers to occasional clouds, which would indicate that clouds are present but not in a significant way, and "NOCLD" is not a standard term in METAR reports. Therefore, "CLR" is the most appropriate and universally understood term for when no clouds are detected below 12,000 feet in an automated station report.