Final answer:
The price elasticity of demand in a linear demand curve varies along the curve; it is elastic at high prices and inelastic at low prices, thus, none of the provided options directly apply without additional context.
Step-by-step explanation:
If demand is linear (a straight line), then the price elasticity of demand cannot be uniformly categorized as perfectly elastic, perfectly inelastic, unitary elastic, or elastic without additional context. In a linear demand curve, elasticity varies at different price points since the percentage change in quantity demanded relative to a percentage change in price is not constant along the curve. Typically, a linear demand curve will be elastic at high price levels (where a small change in price leads to a large change in quantity demanded), and inelastic at low price levels (where a large change in price leads to a small change in quantity demanded). Therefore, the answer is not clearly defined by the options provided and would depend on the specific portion of the demand curve being examined.
Elastic demand or elastic supply indicates that the quantity demanded or supplied is highly responsive to changes in price, with an elasticity greater than one. Inelastic demand or supply suggests a lower responsiveness, with an elasticity less than one. Unitary elasticity indicates proportional responsiveness, where the percentage change in quantity demanded or supplied equals the percentage change in price.