Answer:
a. Mesozoic
Explanation:
Out of these options, the Mesozoic Era is the era of geological time that lasted the longest. This era lasted roughly from 252 to 66 million years ago. The term "Mesozoic" means "middle life" and is divided into the Triassic, Jurassic and Cretaceous. This era also saw the gradual rifting of Pangaea into separate landmasses.
