The answer’s b, the Ordovician Extinction.
A.) is an explosion of growth from flora and fauna. With tons of diverse species.
B.) Is where 60 to 70 percent of species die on Earth due to a rapidly cooling atmosphere. And by the looks of the graph, the percentage lost looks to be around 50 to 60 percent.
C.) the Perm-Triassic Extinction Event is also known as the Great Dying, where around 96% of the worlds species went extinct. This is not at all shown by the graph.
D.) is a forming of the Appalachian mountains or something to do with that. It’s not the answer.
So the answer is b. Hope this helps!
