Why would a researcher use a primary source instead of a secondary source when analyzing a historical event?

explanation:

ad the excerpt and i will gladly answer

according to the map, most industrialization in europe occurred in the northwest.

the production of coal and lignite deposits was profitable throughout western europe.

the building of railroads transport goods throughout europe.

according to the map, the population trend indicates that more people are moving into cities.

northwest

coal and lignite depostis

railroads

cities