Final answer:
The Radical Republicans in Congress sought to gain voting rights for the newly freed slaves after the Civil War, as part of their effort to transform Southern society and ensure a strict reintegration of Confederate states into the Union.
Step-by-step explanation:
Radical Republicans' Goals After the Civil War
The major goal of the Radical Republicans in Congress after the Civil War was to ensure the newly freed slaves gained voting rights. This motive was part of a broader agenda to reconstruct the South and to create a new voting bloc that would support Republican ideals and policies. Their plans diverged significantly from those of President Andrew Johnson, who was more inclined to quickly reincorporate the Southern states into the Union on lenient terms. The Radical Republicans wanted to transform Southern society, end the plantation system, and especially ensure that voting rights for the freedmen were established.
President Lincoln had sought a swift reunion of the states with his lenient Ten Percent Plan, whereas the Radical Republicans aimed for a more stringent reintegration with protections for the freed slaves. The Radicals saw the Southern states' attempted secession as an act that forfeited their rights, requiring them to seek readmission to the Union under terms set by Congress.
To sum up, the answer to the student's question is A) gain voting rights for the newly freed slaves.