Among the four basic market structures, a monopoly gives the business the GREATEST control over price because it is the sole provider of a product or service in the market. In a monopoly, there are no direct competitors, allowing the company to set prices without the constraint of market competition.
On the other hand, perfect competition gives the business the LEAST control over price. In perfect competition, there are many small firms competing in the market, and they are price takers, meaning they have no control over the price and must accept the market price as given.
So, the correct answers are:
GREATEST control over price: a. Monopoly
LEAST control over price: d. Perfect competition