The price elasticity of demand for a vertical demand curve is: a. perfectly elastic. b. unitary elastic. c. perfectly inelastic. d. elastic.

A **vertical demand curve** represents a situation where the quantity demanded remains unchanged regardless of any change in price. This implies that consumers are **completely unresponsive** to price changes. **Price Elasticity of Demand (PED)** measures how much the quantity demanded of a good responds to a change in its price. The PED is calculated as: \[ \text{PED} = \frac{\% \text{ Change in Quantity Demanded}}{\% \text{ Change in Price}} \] For a vertical demand curve: - **Quantity demanded does not change** when the price changes. - Therefore, the **percentage change in quantity demanded is 0**. - This results in a PED of **0**, indicating **perfectly inelastic** demand. **Summary of Options:** - **a. Perfectly elastic**: PED is infinite (horizontal demand curve). - **b. Unitary elastic**: PED is exactly 1. - **c. Perfectly inelastic**: PED is 0 (vertical demand curve). - **d. Elastic**: PED is greater than 1. **Correct Answer:** c. perfectly inelastic.