Final answer:
A perfectly inelastic demand curve is depicted as a vertical line on a graph, indicating that the quantity demanded is constant, regardless of price changes. It represents a situation of zero elasticity in which consumers' demand for a product is not affected by price adjustments.
Step-by-step explanation:
A perfectly inelastic demand curve is represented by a vertical line at a given quantity, which means that the quantity demanded doesn't change regardless of the price level. This is described as a zero elasticity situation where the demand for a product is completely unresponsive to price changes. In other words, consumers will buy the same amount of a good or service no matter how much the price fluctuates.