Which of the following events immediately preceded the the Cenozoic era in which mammals became the dominant animal grou

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Which of the following events immediately preceded thethe Cenozoic era in which mammals became the dominant animal groupon earth?
Group of answer choices
a) The Cambrian Explosion caused the majority of species to goextinct.
b) The Permian mass extinction caused the previously dominantspecies to be eliminated.
c) The Cretaceous mass extinction caused the extinction of thedinosaurs.
d) Mammals have always been the dominant species since theevolution of the first eukaryotic cell.