Final answer:
The 13th, 14th, and 15th amendments significantly strengthened federal authority by abolishing slavery, ensuring citizenship and equal protection, and extending voting rights regardless of race, which reduced state sovereignty in these areas.
Step-by-step explanation:
When we read the 13th, 14th, and 15th amendments and examine their impact on the power balance between the states and the federal government during the Reconstruction era, it becomes clear that there was a significant shift. With the 13th Amendment, slavery was officially abolished throughout the United States, while the 14th Amendment ensured citizenship and equal protection under the law for all, regardless of race, and imposed constraints on the states' ability to infringe upon these protections. The 15th Amendment extended voting rights to all men, regardless of race, thus increasing Black political power. Together, these amendments strengthened federal authority by placing new requirements on the states and granting Congress the power to enforce these requirements, thereby reducing state sovereignty over these matters.
The correct answer to how these Reconstruction amendments changed the power balance is B) The amendments strengthened federal authority. They mandated certain state constitutional reforms, established conditions for readmission of Confederate states into the Union, and expanded the number and type of federal protections against racial discrimination, especially in voting rights. This shift toward federal control was part of a larger trend that had been emerging in the 19th century, emphasizing the power of the national government over the states, particularly in matters of civil rights.