A. The 15th Amendment.
The 15th Amendment (1870) was the law that granted African American men the right to vote for the first time in the U.S. Ever since it was enacted, Southern states tried to put conditions and obstacles to deny them such right. For example, election officials imposed black people poll taxes, they'd tell them that they had gotten the date, time or polling place wrong, that they had filled out an application incorrectly or they had to recite the whole Constitution or to take literacy tests in order to be allowed to vote. To threaten them with violence was also common.