1) God provided atonement for Adam and Eve's sin by killing an animal and using its skin to clothe them, representing the need for an innocent sacrifice to cover human sin and shame. 2) Only God can provide a satisfactory atonement and covering for human sin through the sacrifice and shedding of blood, as seen in God accepting Abel's blood sacrifice over Cain's non-blood offering. 3) Jesus Christ's death on the cross made atonement for human sin by satisfying God's justice, with Jesus as the innocent substitute who endured punishment in our place through his sacrificial death.