What is similar to the guilds of the Middle Ages?

1. government

2. landowners

3. corporations

4. labor unions

A guild is an association of artisans or merchants who oversee the practice of their craft in a particular town. The earliest types of guild were formed as confraternities of tradesmen. They were organized in a manner something between a professional association, trade union, a cartel, and a secret society.

After researching each word, I would say (4) Labor unions