When a Good Has a Unitary Price Elasticity, Consumer Expenditures

When a good has a unitary price elasticity, consumer expenditures for the good

A) change in the same direction as a price change.
B) change in the opposite direction to a price change, but not necessarily by the same percentage as the price change.
C) do not change when the price of the good decreases.
D) change in the opposite direction and by the same percentage as any price change.