Final answer:
The demand curve facing a perfectly competitive firm is perfectly horizontal (E), indicating that the firm can sell any quantity it wants at the market price without affecting the price itself, as it is a price taker in a perfectly competitive market.
Step-by-step explanation:
The demand curve facing a perfectly competitive firm is often described in economics. Students might encounter this concept in their studies, particularly when comparing different market structures. In a perfectly competitive market, each firm perceives the demand for its goods as being perfectly elastic. This concept is contrasted with a monopolistically competitive firm, which faces a demand curve that is an intermediate case between perfect competition and monopoly, and a monopoly, where the demand curve is the same as the market demand curve.
This means that the firm can sell as much as it wants at the market price, and the price does not change with the quantity supplied by the firm. The perfectly elastic demand curve represents the fact that the firm is a price taker and can sell its product at the prevailing market price with no influence on the price itself.