This occupational classification most likely included doctors, lawyers, and dentists in 1880.
agriculture, fisheries, and mining
trade and transportation
manufacturing and mechanical
professional service

Option: Professional service

Explanation:

The doctors, lawyers and dentists in 1880 included in the professional service because they were the practitioners. The professional service occupies the occupants from arts and science that requires certification. They require skills and knowledge to perform work and come under the tertiary sector of the economy.  

c. troops marched forward in close formation against newer, more accurate weapons

the communist manifesto is an 1848 political pamphlet by the german near the end of the manifesto, the authors call for a "forcible overthrow of all existing social conditions",  ..