Which of these lists is in the correct order, starting at 550 mya to 50 mya:
O Cambrian explosion, radiation of reptiles, K-Pg extinction, radiation of mammals
O Permian extinction, radiation of reptiles, radiation of mammals, evolution of humans
O Cambrian explosion, multicellular organisms first appear, radiation of reptiles, Permian extinction
O Carboniferous period, radiation of reptiles, Permian extinction, radiation of mammals
