Which best explains how gravity contributes to the formation of layers in protoplanets?

Gravity attracts materials and causes compaction, which produces heat and leads to the melting, sinking, and rising of materials.
Gravity causes materials to undergo radioactive decay, which produces heat and leads to the melting, sinking, and rising of materials.
Gravity absorbs heat, which cools materials and causes them to sink and rise.
Gravity releases heat into space, which cools materials and causes them to sink and rise.