Answer :
Answer: d. The demand curve for a purely competitive firm is perfectly elastic, but the demand curve for a purely competitive industry is downsloping.
Explanation:
In a purely competitive market, all the firms are selling the same product so there is a lot of competition. The market sets the price in this industry at the point where quantity demanded equals quantity supplied and the demand curve for the whole industry is downward sloping.
When it comes to the demand curve for the individual firm however, it is elastic because price is not set by the firm. This perfectly elastic demand shows that if the firm tries to sell at a price that is different from the market, quantity demanded from that firm would change by infinity because people would prefer the market price.