Final answer:
The correct answer is (a) Universal suffrage
Step-by-step explanation:
After the Civil War, Congress focused on restructuring the defeated Confederate states and securing civil rights for formerly enslaved individuals. A "republican form of government" as established in this period emphasized universal suffrage, at least for all men regardless of race, as evidenced by legislative efforts and constitutional amendments. Specifically, the Reconstruction Amendments (the 13th, 14th, and 15th Amendments) were crucial to this effort. The Thirteenth Amendment abolished slavery, the Fourteenth Amendment guaranteed equal protection under the law, and the Fifteenth Amendment aimed at prohibiting the denial of the right to vote based on race, color, or previous condition of servitude.
In relation to the actions of Congress post-Civil War, the correct answer to the provided question is (a) Universal suffrage. This reflects the push by Radical Republicans and others to extend voting rights to formerly enslaved persons, as well as the broader agenda to secure a more inclusive democracy that went beyond the propertied elite. The option avoids the incorrect responses associated with vestiges of the old order, such as slavery, monarchical rule, or strict segregation, all of which were antithetical to the evolving conception of a republic during Reconstruction.