a downward sloping demand curve means that?

Analyze the question: A downward sloping demand curve shows the relationship between price and quantity demanded. It slopes from top-left to bottom-right.

Explain the concept: This is the law of demand. When the price of a good falls, the quantity demanded rises, and when the price rises, the quantity demanded falls, all else being equal (ceteris paribus). Price and quantity demanded move in opposite directions.

Evaluate each option:

• A. Total revenue declines as price is lowered. This is not always true. Total revenue depends on elasticity. If demand is elastic, lowering the price increases total revenue. A downward slope alone does not tell us this.
• B. Demand falls as output rises. This mixes up terms. Output is a supply-side idea, and "demand falls" confuses a change in demand (a shift of the curve) with a change in quantity demanded (a movement along it).
• C. Demand falls as output falls. This is also incorrect for the same reasons. It has no link to the slope of the demand curve.
• D. Price must be lowered to sell more. This matches the law of demand. To get consumers to buy a larger quantity, the seller must reduce the price. This is exactly what the downward slope shows.

Answer: The correct option is D.

Tip: In demand questions, look for the option that states the inverse relationship between price and quantity (price down, quantity up). Also remember that a movement along the curve is caused by a price change, while a shift of the curve is caused by other factors such as income, tastes, or the prices of related goods.