Which era includes the Triassic, Jurassic, and Cretaceous periods?

• A. Mesozoic Era
• B. Precambrian Era
• C. Paleozoic Era
• D. Cenozoic Era

Answer: (A)

The key idea here is that Triassic, Jurassic, and Cretaceous are all periods within one era—the Mesozoic. This era, often called the middle life era, stretched roughly from 252 to 66 million years ago and is famous for the age of dinosaurs and major dinosaur diversification. The Mesozoic sits between the older Paleozoic and the younger Cenozoic, which marks the rise of mammals after the extinction event that ended the Mesozoic. The Precambrian represents a much earlier time before complex life, so it predates these periods, while the Paleozoic is the era that comes before the Mesozoic and ends with a mass extinction, and the Cenozoic comes after the Mesozoic.