Answer:
Appoint six Supreme Court justices
The answer would be sound waves.
Hope this helps!
In economics there are four different types of market structures. They are as followed:
1) Perfect competition- This allows for businesses to compete against each other for consumers.
2) Monopoly- This is when one business or corporation corners a market. This occurs when a business is the only supplier of a good/service.
3) Oligopoly- This is when a small amount of businesses control a market/product.
4) Imperfect competition
In your question then, the correct answers are : Monopoly, perfect competition, and oligopoly.
