I'd go with A. Mesozoic Scientist divide the Mesozoic era in three periods : the Triasic, Jurassic and Crestaceous. Hope this helps
A: Mesozoic ;
The dinosaurs lived during the Mesozoic Era, which lasted from about 252 to 66 million years ago. This era is known as the 'Age of Reptiles' and is divided into three periods: Triassic, Jurassic, and Cretaceous. The appropriate answer to the question is A. Mesozoic.
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