The correct answer is Fingers, hair, and clothing often got caught in the gears and belts of machines.
The central idea of this passage is that working conditions were not ideal for workers during the Industrial Revolution. In order to support this, a person needs to use specific facts or information to prove their claim. In this case, the only answer choice that gives specific details as to why the working conditions were not ideal was the last answer choice. This is why option number 4 is the correct answer.