Answer:
B. The passage of the Fifteenth Amendment
Step-by-step explanation:
Fifteenth amendment of the constitution of the United States emphasized the right to vote to all the citizens irrespective of the race or but the word black was avoided. After much-debated discussions and ratification in it, it was passed in 1870. Finally, the Republicans passed it. However, the conditions were stable in the north but the south was on the violent path where black people were killed when they tried to use their right.