Explanation:

- In a monopoly, the firm is the sole supplier of its product. The demand curve reflects the price consumers are willing to pay at different quantities.

- Option 1, upward sloping: This would imply higher prices increase demand, which is unusual in standard economics as it contradicts the law of demand.

- Option 2, downward sloping: The correct answer. This represents how a monopoly can set higher prices with a lower quantity sold, showing an inverse relationship between price and demand.

- Option 3, horizontal: This would indicate perfect elasticity, which is typical in perfectly competitive markets, not monopolies.

- Option 4, vertical: That would mean price is completely inelastic, unresponsive to changes in quantity, which doesn't describe a monopolistic demand.