The first form of life arose slowly from non-living molecules through the evolutionary process :
Protobionts
Abiogenesis
Microsphere
Coacervates
As we have already studied in Biological Evolution -
Abiogenesis is the first form of life that arose slowly through evolutionary forces from non-living molecules is accepted by the majority and was originated about 2000 million years ago. Hence, the correct option is (b).