The correct option is C Mesozoic
The second era in the Phanerozoic eon is the Mesozoic era. It is also called the golden age of reptiles, as it witnessed the emergence of a huge diversity of reptiles. This era is divided into three periods - Triassic, Jurassic and Cretaceous. In the Jurassic period, giant reptiles like dinosaurs and toothed birds like Archeopteryx dominated Earth.