Which was a major cause of environmental pollution in American cities during the late 1800s?

Awastewater discharge from hydroelectric power plants
Bchemicals used in dry cleaning shops
Clarge numbers of horses used for transportation
Ddust storms blowing in from the Great Plains

Verified Answer :

A major cause of environmental pollution in American cities during the late 1800s was "a. wastewater discharge from hydroelectric power plants" since this was a major issue in the Industrial Revolution. 

A) wastewater discharge from hydroelectric power plants was a major cause of environmental pollution in American cities during the late 1800s.