Rock Mountain Revolution took place after the Mesozoic era.

The Rock Mountain Revolution, also known as the Laramide orogeny, refers to a period of mountain-building that occurred during the Late Cretaceous and Paleogene periods in western North America. This event led to the formation of the Rocky Mountains and other associated mountain ranges.

Explanation:

1. The Mesozoic era:
The Mesozoic era is a geological time period that spans from approximately 252 to 66 million years ago. It is divided into three major periods: the Triassic, Jurassic, and Cretaceous. This era is characterized by the dominance of dinosaurs, the rise of flowering plants, and the breakup of the supercontinent Pangaea.

2. The Paleozoic era:
The Paleozoic era precedes the Mesozoic era and extends from approximately 541 to 252 million years ago. It is divided into six periods, including the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian periods. This era is known for the diversification of life, including the emergence of fish, amphibians, reptiles, and early land plants.

3. The Proterozoic era:
The Proterozoic era is a geological time period that extends from approximately 2.5 billion to 541 million years ago. It is characterized by the development of complex life forms, including multicellular organisms and the first appearance of eukaryotic cells. This era also witnessed the formation of supercontinents and significant changes in Earth's atmosphere.

4. The Coenozoic era:
The Coenozoic era, also known as the Cenozoic era, is the current geological era. It began approximately 66 million years ago and continues to the present. This era is marked by the diversification and dominance of mammals, the evolution of primates and humans, and significant climatic changes, including ice ages.

5. The Rock Mountain Revolution:
The Rock Mountain Revolution, or Laramide orogeny, occurred during the Late Cretaceous and Paleogene periods, which fall within the Mesozoic era. It was a major tectonic event that resulted in the uplift and deformation of the western North American continent. The formation of the Rocky Mountains and other associated mountain ranges, such as the Sierra Nevada and the Cascade Range, is attributed to this mountain-building event.

Therefore, the correct answer is option B) Mesozoic era, as the Rock Mountain Revolution occurred after this era.