How did the federal government try to protect the rights of blacks during congressional reconstruction?
a. it supported the ku klux klan and other southern groups.
b. it sent soldiers south to ensure blacks could exercise their rights.
c. it forced southern legislatures to appoint redeemer democrats.
d. it instituted black codes and jim crow laws in all southern states.

b. It sent soldiers south to ensure blacks could exercise their rights.

Explanation:

The reconstruction was a period of American history that lasted from 1865 to 1877. The term has two applications: the first applies to the entire history of the entire country from 1865 to 1877 after the Civil War; the second, to the attempted transformation of the 11 ex-Confederate states from 1863 to 1877, as ordered by Congress. The reconstruction put an end to the remnants of Confederate nationalism and put an end to slavery, making the new slaves free citizens with civil rights seemingly guaranteed by three new constitutional amendments. Three visions of the memory of the civil war appeared during Reconstruction: the vision of reconciliation, which was rooted in coping with death and the devastation of war had brought; the vision of white supremacy, which included terror and violence; and the vision of emancipation, which sought full freedom, citizenship and constitutional equality for African Americans.

regarding the law, the 15th amendment was specifically designed thinking in the rights of black free men.

even though ratified on february 3, 1870, the promise of the 15th amendment would not be fully applied for a long time.poll taxes and literacy tests would allow southern states disenfranchise african americans. only in 1965 the voting rights for african americans would be actually able to vote in the south.

in 1965, president johnson signed the voting rights act, which aimed to overcome legal barriers that prevented african americans from voting as it was guaranteed by the 15th amendment to the u.s. constitution.