The correct answer is D) The relative sizes of the areas affected by each level of unemployment.
The information might a geographer be able to convey more clearly than the economic historian is the relative sizes of the areas affected by each level of unemployment.
A geographer study the land, the region, the natural resources of different places, and the people who lived in those regions and how they are affected by the environment, mountains, rivers, lakes, and the soil. They also study the economic, political and culture of these places and how people are influenced by them. That is why the geographer can establish the areas affected by each level of unemployment during the Great Depression in the United States that began in October 1929, after the crash of the US stock market.
The other options of the question were A) The percentage of each state’s population that was unemployed, B) The level of unemployment in each state; and C) The years when unemployment was worst in each area.