Final answer:
The b. railroad industry most likely felt the greatest impact from the Interstate Commerce Act of 1887.
Step-by-step explanation:
The industry that most likely felt the greatest impact from the progressive regulation imposed by the Interstate Commerce Act of 1887 was the railroad industry. The act required railroads to establish standard fares and publish these rates, preventing discriminatory pricing practices that disadvantaged small farmers. It also created the Interstate Commerce Commission to regulate the business practices of railroads.
The railroad industry, being a major player in transportation during that time, would have been directly affected by this regulation. The act sought to prevent the railroads from charging excessive or unfair prices for their services, protecting consumers and ensuring a level playing field in the industry.