Final answer:
The demand for open-heart surgery is perfectly inelastic when the demand curve is vertical, meaning quantity demanded remains unchanged regardless of price changes. The correct option is D.
Step-by-step explanation:
If the demand curve for open-heart surgery is vertical for people with serious heart conditions, then the demand for open-heart surgery is perfectly inelastic with respect to price. When a demand curve is perfectly inelastic, it means that the quantity demanded does not change regardless of any changes in price.
Even significant fluctuations in the cost of surgery will not affect the number of surgeries sought by those with serious heart conditions, because this type of surgery is often essential for survival, and considering its urgent and life-saving nature, its demand will remain constant irrespective of price.
While a perfectly elastic demand curve is represented by a horizontal line, where the quantity demanded is infinitely responsive to price changes, a perfectly inelastic demand curve is depicted as a vertical line, as shown in Figure 5.5 – Zero Elasticity.
This figure demonstrates that there is zero percentage change in quantity demanded, no matter the alterations in price. In contrast with perfectly elastic situations where consumers are highly sensitive to price changes and will adjust their quantity demanded greatly in response to price shifts, a perfectly inelastic demand curve illustrates a scenario where consumers will demand the same amount of a good or service at any price point.