Which statement is TRUE?

a. Nominal GDP is calculated using prices that do not change over time.
b. Real variables have been adjusted for changes in prices.
c. Nominal variables have been adjusted for changes in prices.
d. An increase in nominal GDP automatically means we have produced more.

b. Real variables have been adjusted for changes in prices. 

Explanation:

Nominal GDP = output × current year prices.

Real GDP = output × base year prices.

Nominal GDP is calculated using current year prices, therefore, the prices change overtime due to inflation. An increase in nominal GDP doesn't automatically mean we have produced more. It might mean price increased. It is when output increases that we have produced more.

Real GDP has been adjusted for inflation or changes in price. Real GDP is calculated using prices that do not change over time. 

I hope my answer helps you

1) the stages a new product goes through from beginning to end, i.e., the stages that a product passes through from introduction through growth, maturity, and decline. 2) the time from initial research and development to the time at which sales and support of the product to customers are withdrawn. 3) the period of time during which a product can be produced and marketed profitably.

                                          hope it