Answer:
He developed theories on how power structures in society keep people under control.
Explanation:
The correct answer is: A. Manufacturing goods with interchangeable parts
Manufacturing goods with interchangeable parts was made possible after Eli Whitney envisioned an entire system for transforming a craft performed by skilled artisans into a process performed by unskilled workers. This means each worker would do just one thing.
A secondary source is a description coming from someone who wasn't there and didn't truly experience the event. Since the source contains a soldier's description rather than the soldier writing it him/herself The source is a secondary source. Now since the source obtained it directly from the soldier the source be A. a secondary source with an understandable point of view.