Final answer:
The price elasticity along a perfectly horizontal demand curve is infinite, signaling that consumers are willing to buy any quantity at a specific price, and any price change results in an infinite response in quantity demanded.
Step-by-step explanation:
The student's question relates to the concept of price elasticity of demand, which 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. When a demand curve is perfectly horizontal, it represents a case of perfectly elastic demand. This means that consumers are willing to buy an infinite quantity at a specific price (P), but any deviation from this price causes the quantity demanded to drop to zero or surge to infinity. Therefore, the price elasticity along a perfectly horizontal demand curve is infinite, because the quantity demanded is extremely responsive to even the smallest price change.