In perfectly competitive market, the demand curve of a firm is?

Perfectly elastic.

The correct answer is Option (4) → Perfectly elastic.

In a perfectly competitive market, there are many buyers and sellers, and each firm sells a homogeneous product at a uniform market price.

• Since the price is determined by industry demand and supply, a single firm is a price taker, not a price maker.

• The firm can sell any quantity of output at the prevailing market price, but if it charges even slightly higher, buyers will switch to other firms.

Thus, the demand curve faced by an individual firm is a horizontal straight line at the market price — i.e., perfectly elastic (elasticity = ∞).