A. Doing what God forbids. Eating the forbidden fruit. Because they did not believe what God had said. The devil tempted Eve, and she gave the fruit to Adam. He represented all his posterity.
All mankind is born in a state of sin and misery.
A sinful nature. The anger and judgement of God. Our hearts must be changed before we can be fit for heaven. The Holy Spirit alone. A. None can be saved through the covenant of works.