Which of the following statements is true?

a. The inclusion of intermediate goods and services into GDP calculations would underestimate our nation’s production level.

b. The expenditures approach sums the compensation of employees, rents, profits, net interest, and nonincome expenses for depreciation and indirect business taxes.

c. Real GDP has been adjusted for changes in the general level of prices due to inflation or deflation.

d. Real GDP equals nominal GDP multiplied by the GDP deflator.