Correct Answer: Both the assertion and reason are correct and related.

Solution : The correct answer is (A) Both the assertion and reason are correct and related.

The assertion states that the demand for a product is perfectly inelastic when the quantity demanded remains constant regardless of price changes. This is correct. Perfectly inelastic demand means that the quantity demanded does not change at all in response to price changes. Regardless of whether the price increases or decreases, the quantity demanded remains constant.

The reason states that perfectly inelastic demand occurs when the price elasticity of demand is zero. This is also correct and supports the assertion. Price elasticity of demand measures the responsiveness of quantity demanded to changes in price. When the price elasticity of demand is zero, it indicates that a change in price has no effect on the quantity demanded. This aligns with the concept of perfectly inelastic demand, where the quantity demanded remains constant regardless of price changes.

Therefore, both the assertion and reason are correct and related. Perfectly inelastic demand occurs when the quantity demanded remains constant regardless of price changes, and this corresponds to a price elasticity of demand of zero.