A demand curve parallel to the Y-axis indicates

A demand curve that is parallel to the Y-axis indicates a perfectly inelastic demand. In this case, changes in the price of a product do not affect the quantity demanded by consumers at all. No matter what the price of the product is, consumers will always buy the same amount. For example, let's consider insulin, a life-saving medication for people with diabetes. The demand for insulin is likely to be perfectly inelastic because people with diabetes require a certain amount of insulin to survive, and they are willing to pay whatever price is necessary to obtain it. In contrast, if a demand curve is steep and close to the Y-axis, it indicates a perfectly elastic demand, where consumers are highly sensitive to changes in price, and a small change in price can lead to a large change in the quantity demanded. The other two options, fairly elastic and fairly inelastic demand, refer to demand curves that are less extreme than perfectly elastic or perfectly inelastic. A fairly elastic demand curve indicates that consumers are somewhat sensitive to changes in price, while a fairly inelastic demand curve indicates that consumers are somewhat less sensitive to changes in price.