Jacob Riis, Upton Sinclair, Ida Tarbell, and Lincoln Steffens were all: O A. Republican politicians.
B. Robber barons.
O C. Famous muckrakers.
O D. Former Confederates.

c) famous muckrakers

Explanation:

the difference is that white collar worker performs skills like worker as a scientist or well blue collars do physical work and they do services like being a cook.

the tariff was created to protect industry in the northern part of the united states. industries in the north were being driven out of business by imported goods that were priced at a low rate. the goal was to protect these industries   by taxing the goods.