Final answer:
The correct answer is option d. A perfectly inelastic supply curve is represented by a vertical line, showing that the quantity supplied does not change regardless of price changes. It's the characteristic of suppliers offering a fixed amount of a good or service at any price.
Step-by-step explanation:
The student is asking about the characteristics of a perfectly inelastic supply curve. In economics, when we refer to a supply curve being perfectly inelastic, it means that the quantity supplied does not change regardless of the price level. According to the reference provided, a perfectly inelastic supply curve is represented graphically by a vertical line. This vertical representation shows that producers are willing and able to sell the same quantity of a good whatever the price might be.
For the perfectly inelastic demand curve, a vertical curve also represents that consumers will demand a certain quantity irrespective of the price. Meanwhile, a perfectly elastic supply or demand curve is depicted by a horizontal line, indicating that any amount will be supplied or demanded at one specific price, but the quantity changes dramatically with even a slight variation in price.