Correct Answer: Both the assertion and reason are true, and the reason is a correct explanation of the assertion.

Solution : The correct answer is (a) Option A Both the assertion and reason are true, and the reason is a correct explanation of the assertion.

The downward-sloping demand curve can be explained by both the substitution effect and the income effect. The substitution effect occurs when the relative price of a good changes, leading consumers to substitute towards the relatively cheaper alternative. This effect contributes to the downward slope of the demand curve. Additionally, the income effect reflects changes in purchasing power due to price changes. When the price of a good decreases, consumers experience an increase in real income, which can lead to an increase in the quantity demanded. Conversely, when the price of a good increases, consumers' real income decreases, resulting in a decrease in the quantity demanded. The combination of the substitution effect and income effect leads to the overall downward-sloping demand curve.