Do you think it is:
1. The period about 65 million years ago, when an impact is thought to have led to the extinction of the dinosaurs
2. The time before planetesimals finished accreting into planets, during which many growing planetesimals must have shattered in collisions
3.The first few hundred million years after the planets formed, which is when most impact craters were formed
4. The time during which heavy elements condensed into rock and metal in the solar nebula
