What is the term for groups of craftspeople such as shoemakers who in the middle ages sought to improve their incomes and working conditions?

I believe the answer is Craft-Guilds.
The craft-guilds allow the crafts people to gather up and set a standard price of their service in order to bring out more value for their job.
On top of that, crafters that belong within the same guilds could work together on large projects that usually bring way more profit compared to their day to day transaction.

A group of workers that came together to improve working conditions and incomes is called a union. They first appeared in what is known as the High Middle Ages in Italy and Spain.

The answer would be option a , b, and c.