Which civilization invented the concept of zero and developed an accurate calendar system?

u.s.a

china

india

and

japan

pope john paul ii ( his real name is karol wojtyla) and lech walesa ( the leader of the solidarity movement ) were both born in poland.

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.