Okun's Law illustrates the relationship between:

Okun's Law illustrates the relationship between the output gap and cyclical unemployment, making the selection of this answer accurate. This economic principle suggests that when the economy is functioning below its full potential (the output gap), unemployment tends to rise. Specifically, for every 1% increase in the unemployment rate above the natural rate, a corresponding decrease in GDP of approximately 2% is expected, demonstrating how closely intertwined economic output and unemployment are. This relationship helps policymakers understand how changes in employment levels can affect overall economic growth and vice versa.

The other options relate to different economic principles; for instance, the inflation rate and employment rates pertain more closely to the Phillips Curve, while the money supply and interest rates relate to monetary policy frameworks. The last option discussing the amount of goods in supply versus demand pertains to basic supply and demand theory, which does not directly connect to the concepts encompassed by Okun's Law.