The correct answer is A. Pure competition.
Step-by-step explanation
Pure competition is a concept that refers to a business model in which several small sellers offer their products in a common market. This situation has the peculiarity that no seller has total control or influence on the market price, on the contrary, he must accept the market price that is determined by the supply of the product offered by all sellers and the total demand for the product from all buyers. An example of this trade model is an online auction because in this scenario none of the sellers has control over the value or demand of the products but must accept the price determined from the amount of supply of other sellers and buyer demand. So the answer is A.