Which of these is the best-known symbol of Christianity?

The Christian cross, seen as a representation of the instrument of the crucifixion of Jesus, is the best-known symbol of Christianity.

In Christianity, communicants of the Oriental Orthodox and Eastern Orthodox Churches are expected to wear a cross necklace at all times; these are ordinarily given to believers at their baptism.

Although Christians accepted that the cross was the gallows on which Jesus died, they had already begun in the 2nd century to use it as a Christian symbol. During the first three centuries of the Christian era the cross was "a symbol of minor importance" when compared to the prominence given to it later, but by the second century it was closely associated with Christians and it was already a tradition for Christians to trace repeatedly on their foreheads the sign of the cross.

The oldest extant depiction of the execution of Jesus in any medium seems to be the second-century or early third-century relief on a jasper gemstone meant for use as an amulet, which is now in the British Museum in London. It portrays a naked bearded man whose arms are tied at the wrists by short strips to the transom of a T-shaped cross.

In Christianity, Jesus is the Son of God and in many mainstream Christian denominations he is God the Son, the second Person in the Trinity. He is believed to be the Jewish messiah who is prophesied in the Hebrew Bible, which is called the "Old Testament" in Christianity.