Which of the following pairs is correctly matched?

Answer & explanation

Correct answer: option 3

The correct answer is Option (3) → Demand function — Optimal quantity of a good as a function of its own price

The demand function links the quantity a consumer chooses to the good’s own price, other things unchanged.

Option (1) Demand curve — Price measured along the horizontal axis of the graph — Incorrect. Price is measured along the vertical axis.

Option (2) X in the demand function X = f(P) — Price of the good — Incorrect. X stands for the quantity; P is the price.

Option (3) Demand function — Optimal quantity of a good as a function of its own price — Correct. This is the meaning of the demand function.

Option (4) Independent variable in the demand function — Quantity of the good — Incorrect. Price is the independent variable; quantity depends on it.

NCERT (2026-27): “2.4.1 Demand Curve and the Law of Demand If the prices of other goods, the consumer’s income and her tastes and preferences remain unchanged, the amount of a good that the consumer optimally chooses, becomes entirely dependent on its price. The relation between the consumer’s optimal choice of the quantity of a good and its price is very important and this relation is called the demand function. … The consumer’s demand for a good as a function of its price can be written as X = f (P) (2.12) where X denotes the quantity and P denotes the price of the good.”

“Demand Curve. The demand curve is a relation between the quantity of the good chosen by a consumer and the price of the good. The independent variable (price) is measured along the vertical axis and dependent variable (quantity) is measured along the horizontal axis. The demand curve gives the quantity demanded by the consumer at each price.”