Step 1: Understanding nominal GDP.
Nominal GDP is the total value of goods and services produced in an economy at current market prices, without adjusting for inflation. It is calculated using the prices of the year in which the goods and services are produced.
Step 2: Analyzing the options.
(A) At current prices: Correct. Nominal GDP is measured using the current prices of goods and services in the economy.
(B) At base year prices: This refers to real GDP, which adjusts for inflation by using constant prices from a base year.
(C) At constant prices: This is also related to real GDP, not nominal GDP, as it adjusts for inflation.
(D) None of these: This is incorrect, as the correct answer is (A).
Step 3: Conclusion.
Nominal GDP is measured at current prices. Therefore, the correct answer is (A) At current prices.