The price elasticity of demand is a units-free measure of the responsiveness of __ A. the quantity demanded of a good to a change in its price when all other influences on buying plans remain the same B. the demand for a good when the price of one of it substitutes or a complement of it changes C. the demand for a good when consumers income changes D D. the quantity demanded of a good to a change in the quantity supplied when all other influences on buying plans remain the same

## Step 1<br />The price elasticity of demand is a measure used in economics to show the responsiveness, or elasticity, of the quantity demanded of a good or service to a change in its price. It is a unit-free measure, meaning it does not have units and can be used to compare the elasticity of different goods.<br /><br />## Step 2<br />Option A states that the price elasticity of demand is a measure of the responsiveness of the quantity demanded of a good to a change in its price when all other influences on buying plans remain the same. This is the correct definition of price elasticity of demand.<br /><br />## Step 3<br />Option B refers to the cross-price elasticity of demand, which measures the responsiveness of the demand for a good when the price of one of its substitutes or a complement changes. This is not the definition of price elasticity of demand.<br /><br />## Step 4<br />Option C refers to the income elasticity of demand, which measures the responsiveness of the demand for a good when consumers' income changes. This is not the definition of price elasticity of demand.<br /><br />## Step 5<br />Option D refers to the concept of elasticity of supply, which measures the responsiveness of the quantity supplied of a good to a change in its price. This is not the definition of price elasticity of demand.