Demand Curve of a Firm Is Perfectly Elastic Under: (Choose the Correct Alternative)
Perfect competition
In perfect competition, the firm can sell any amount of goods at the prevailing prices, therefore the demand curve of a firm is perfectly elastic under perfect competition.
Also read:
Elasticity of Demand
Price Elasticity of Supply
Price Elasticity of Demand Formula
Income Elasticity of Demand Formula
The option (a) is correct.