Areliable source
(a) may contain some biased information.
(b) is written from a trustworthy point of view.
(c) is usually a secondary source.
(d) must be a primary source.

A reliable source can be primary or secondary, eliminating answers c and d. If it is truly reliable, then naturally it would not contain biased information, eliminating choice a. Therefore, the only feasible answer is b.

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.

confedracy

supported slavery

upheld the supremacy of federal laws

believed states should be able to nullify federal laws

union

wanted to abolish slavery

supported high tariffs

upheld the supremacy of federal laws