Answer: Option D
Step-by-step explanation: In simple words, perfect competition refers to the market structure in which there are huge number of buyers and sellers and each of them operate at a very small level. All the firms in such industry sells identical products and make normal profits both in short run and long run.
No firm in a perfect competition can influence prices as they each operate at a small level and sells identical goods, therefore, a slight change in price will shift the demand to other firms and the firm charging high prices will eventually go out of the market.
In such a structure , the pries are determined by the market forces of demand and supply.