<span>The names of the three eras identified on the x-axis in model 1 answers are Paleozoic, Mesozoic and Cenozoic. It can be seen from the graph that a mass extinction happened 444 million years ago in Paleozoic era, another happened 254 million years ago at end of Paleozoic era and marked the beginning of Mesozoic era. The final mass extinction happened 65 million years ago at end of Mesozoic era in which dinosaurs went extinct.</span>
B
the probability of an event ( A<span> ), given that another ( </span>B<span> ) has already occurred.
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