If the coefficient of price elasticity of demand of a product is zero, then its demand curve will be

Analyze the question: Elasticity of demand = 0 means perfectly inelastic demand. Quantity demanded does not change at all when price changes.

Concept: Price elasticity of demand (PED) = % change in quantity demanded ÷ % change in price.

• If PED = 0, the % change in quantity is 0 no matter how much price changes.
• This is perfectly inelastic demand.

Graph: By convention, price (P) is on the vertical axis and quantity (Q) on the horizontal axis.

• Since quantity stays fixed at one value while price varies, the demand curve is a vertical straight line.
• A vertical line is parallel to the price axis (the vertical axis).

Checking the options:

• A. Parallel to the quantity axis: this would be a horizontal line, which is perfectly elastic demand (PED = infinity). Wrong.
• B. Parallel to the price axis: a vertical line, which is perfectly inelastic demand (PED = 0). Correct.
• C. Negatively sloped: this is the normal demand curve, with PED between 0 and infinity. Wrong.
• D. Positively sloped: this is not a normal demand curve (it would be a supply curve or a Giffen-type case). Wrong.

Tip: Remember it this way: Zero = vertical (the "I" shape, Inelastic, looks like an upright line), and Infinity = horizontal. Perfectly inelastic goods in real life include life-saving drugs such as insulin, where people buy the same quantity regardless of price.