Explanation:

- Option 1: Oligopoly

- An oligopoly occurs when there are a few dominant sellers in the market.

- Companies often have significant control over prices.

- Common in industries like airlines and automobiles.

- Option 2: Monopoly

- A monopoly exists when there is only one seller and many buyers.

- The seller controls pricing and supply.

- Often seen in utilities like water supply.

- Option 3: Perfect Competition

- Characterized by many sellers and many buyers.

- No single entity can influence the market price.

- Products are typically homogeneous.

- Option 4: Monopsony

- Occurs when there is one buyer and many sellers.

- The buyer influences prices and terms due to their purchasing power.

- Seen in markets like defense procurement or certain labor markets.