Through Jesus Christ is the only way to get eternal life

Romans 5:12-21
Before the law was given, sin was in the world. But sin is not taken into account when there is no law.
But the gift is not like the trespass. For if the many died by the trespass of the one man, how much more did God’s grace and the gift that came by the grace of the one man, Jesus Christ, overflow to the many!
The law was added (brought in) so that the trespass might increase. But where sin increased, grace increased all the more, so that, just as sin reigned in death,so also grace might reign through righteousness to bring eternal life through Jesus Christ our Lord.
Why?
Sin was in the world when Adam was, before the Moses declared the laws.
One man: Adam, another one man is the last Adam; Jesus Christ.
No matter how a man has done his effort, man always has the character of Adam, so man need the gift of God, grace,  to overcome our transgression.
We all have an innate tendency to feel that laws were made to be broken. The fact that something is forbidden actually makes us want to do it more.
How?
No one is righteousness in the world. Through Jesus Christ is the only way to get eternal life.