The correct answer is option 'B' - Mesozoic.

The Jurassic period is a geological period that occurred approximately 201 to 145 million years ago. It is part of the Mesozoic era, which is often referred to as the "Age of Reptiles." The Mesozoic era is divided into three periods: the Triassic, Jurassic, and Cretaceous periods.

The Mesozoic era
- The Mesozoic era is one of the three major eras in Earth's history, preceded by the Paleozoic era and followed by the Cenozoic era. It spanned from approximately 252 to 66 million years ago.
- The Mesozoic era is often called the "Age of Reptiles" because it was a time when reptiles, particularly dinosaurs, were the dominant land animals.
- It is divided into three periods: the Triassic, Jurassic, and Cretaceous periods. Each period is characterized by its own unique geological and biological features.

The Jurassic period
- The Jurassic period is the second period of the Mesozoic era, occurring from approximately 201 to 145 million years ago.
- It was named after the Jura Mountains, a range located between France and Switzerland, where rocks from this period were first studied.
- The Jurassic period is known for its diverse and abundant dinosaurs, including iconic species like the Brachiosaurus, Stegosaurus, and Allosaurus.
- It was also a time of significant evolutionary developments, including the emergence of the first birds and the rise of flowering plants.

Other periods in the Mesozoic era
- The Triassic period is the first period of the Mesozoic era, occurring from approximately 252 to 201 million years ago. It is known for the emergence of the first dinosaurs and the mass extinction event that marked the end of the period.
- The Cretaceous period is the third and final period of the Mesozoic era, occurring from approximately 145 to 66 million years ago. It is known for its diverse dinosaur fauna, including the famous Tyrannosaurus rex, and ended with the mass extinction event that wiped out the dinosaurs.

In conclusion, the Jurassic period belongs to the Mesozoic era, which is known as the "Age of Reptiles." It is the second period of the Mesozoic era and is characterized by its diverse dinosaurs and significant evolutionary developments.