What does an economy experience when it operates below its full-employment capacity?

An equilibrium gap is not a standard term used in economic theory. It may imply a theoretical balance between supply and demand, but it does not specifically relate to the situation of an economy operating below its full-employment capacity. Therefore, it does not accurately describe the economic conditions of underperformance.

An inflationary gap occurs when the actual output exceeds the economy's full-employment capacity, leading to upward pressure on prices due to increased demand. This situation is the opposite of operating below capacity, as it indicates overheating in the economy rather than underutilization.

An expansionary gap suggests that the economy is capable of producing more than its current output level, often due to factors like increased demand or investment. However, this term is not commonly used to describe the state of operating below full-employment capacity, making it an incorrect choice in this context.