Due to the deaths of most of the population, "ordinary farm workers, who had been forced into serfdom previously, shot up by 50%. More bullion among a smaller population meant more wealth across all classes and because the same land was in use and it was now plentiful, it resulted in technological advances as well." - Hank Campbell (found at Science20.com)
About a third of the clergy fell to the Black Death, making answer a. unlikely.
I never found any information stating Peasants migrated into cities for medical care, making answer b. unlikely.
Lower classes benefited from the Black Death economically, therefore c. is my final answer.
Doctors at this time knew nothing about how to cure disease, they also made little to none advancements. Answer d. is very wrong.
C. Ellen’s fiance defeats lochinvar in armed battle
The correct answer is C eliminate unfair business practices.
The Interstate Commerce Act was created in 1887 to tackle railroad monopolies. It set guidelines on how the railroad companies could do business. The act became a law which demanded "just and reasonable" rates; prohibited special rates for individual shippers; prohibited favoritism in rates for shippers, or products; prohibited pooling of traffic and established an Interstate Commerce Commission.