Which of the following industries is a real-world example of monopolies?

The real-world example of a monopoly from the options provided is the **local electricity company with no competitors**. In many regions, utilities such as electricity providers are single providers in their area, meaning they hold a monopoly over that specific market. This can occur due to high infrastructure costs, regulatory issues, or other barriers to entry that prevent competition.

The other options typically have multiple competitors:

- **Commercial airlines** usually compete against one another on various routes.
- **Agricultural vendors** often have many competitors within the market.
- **Fitness centers in a large city** generally face competition from other gyms and fitness facilities.