Macroeconomics 20th Edition by Campbell McConnell,Stanley Brue,Sean Flynn

Exercise 14

The AD curve slopes downward because:
A) per-unit production costs fall as real GDP increases.
B) the income and substitution effects are at work.
C) changes in the determinants of AD alter the amounts of real GDP demanded at each price level.
D) decreases in the price level give rise to real-balances effects, interest-rate effects, and foreign purchases effects that increase the amount of real GDP demanded.