Final answer:
In a perfectly competitive market, there are neither spillover benefits nor spillover costs.
Step-by-step explanation:
In this case, the correct answer would be a) Perfectly Competitive Market. A perfectly competitive market is a market structure where there are many buyers and sellers, and no single participant can influence the price or quantity of goods traded. In such a market, there are neither spillover benefits nor spillover costs, meaning that the benefits and costs of production are internalized by the buyers and sellers.