An elasticity measures –

Correct option is D

The correct answer is (D) How responsive one variable is to another variable

Explanation:
• In economics, elasticity is a fundamental concept used to quantify the degree of responsiveness or sensitivity of one economic variable to changes in another.
• Mathematically, it is expressed as the percentage change in a dependent variable divided by the percentage change in an independent variable.
• For example, Price Elasticity of Demand measures how much the quantity demanded of a good changes when its price changes.
• If a small change in price leads to a large change in quantity demanded, the product is said to be elastic; conversely, if the change in quantity is minimal, it is inelastic.
• This concept helps businesses and policymakers understand how shifts in market conditions, such as taxes or supply shocks, will affect consumer behavior and total revenue.

Information Booster:
• The formula for elasticity is generally $E = \frac{\%\Delta Y}{\%\Delta X}$.
• Unitary elasticity occurs when the percentage change in one variable is exactly equal to the percentage change in the other (Elasticity = 1).
• Perfectly inelastic curves are vertical, meaning the variable does not respond to changes at all.

Additional Knowledge:
• Prices and Inflation (Option A): While related, this refers to macroeconomic stability rather than a specific measure of responsiveness.
• Law of Supply (Option B): This is a qualitative statement that price and quantity supplied move in the same direction, whereas elasticity provides the quantitative measure.
• Stock Market Influence (Option C): While elasticity exists in finance, 'elasticity' as a general term is defined by the relationship between any two interdependent variables.