What was a reason why people left family farms to move to the city?
Factory work was controlled by rigid schedules, with no slow seasons.
Factory work was easier, and the schedules were flexible.
Factory work paid wages in cash, which was not always the case on farms.

I would say the last one, Factory work paid wages in cash

Explanation: Factory work did have some confusing and complicated functions to it so B is out, and sometimes it could have times where they have low supply on materials so that could be considered having a slow season so A would be out.

factory work paid wages in cash

Explanation:

the  wilmot proviso  was designed to eliminate  slavery  within the  landacquired as a result of the mexican war (1846-48). fearing the addition of a pro-slave territory, pennsylvania congressman david  wilmot proposedhis amendment to the bill.