Option 1 -> Nominal GDP measures goods and services at current market prices, not constant prices.
Option 2 -> Inventory refers to the stock of goods held by businesses, unrelated to price measurement.
Option 3 -> Inflation is the rate at which the general price level increases, not a valuation method.
Option 4 -> Real GDP measures goods and services at constant prices from a base year.
Hence, Option 4: Real GDP -> Real GDP is calculated by valuing goods and services at constant prices (base year prices), which removes the effect of inflation and allows for accurate comparison of economic output over time. Unlike Nominal GDP which uses current prices, Real GDP provides a true measure of economic growth by isolating changes in quantity from changes in prices. -> correct