The correct answer is: c) Tertiary.
The Tertiary period is a geological period that lasted from 66 million to 2.6 million years ago. It is the third and final period of the Cenozoic Era. The Tertiary period is often referred to as the “Age of Mammals” because it was during this time that mammals diversified and became the dominant land animals.
The Tertiary period is also known for its rich oil and coal resources. These resources were formed from the remains of plants and animals that lived during the Tertiary period. The oil and coal resources in Assam are thought to have formed from the remains of plants that lived in swamps and marshes.
The Pleistocene period is a geological period that lasted from 2.6 million to 11,700 years ago. It is the first period of the Quaternary Era. The Pleistocene period is often referred to as the “Ice Age” because it was during this time that glaciers covered much of the Earth’s surface.
The Jurassic period is a geological period that lasted from 201.3 million to 145.5 million years ago. It is the second period of the Mesozoic Era. The Jurassic period is often referred to as the “Age of Dinosaurs” because it was during this time that dinosaurs reached their peak diversity and abundance.
The Cretaceous period is a geological period that lasted from 145.5 million to 66 million years ago. It is the last period of the Mesozoic Era. The Cretaceous period is often referred to as the “Age of Dinosaurs” because it was during this time that dinosaurs reached their peak diversity and abundance. However, the Cretaceous period is also known for the mass extinction event that wiped out the dinosaurs.
In conclusion, the correct answer is: c) Tertiary. The Tertiary period is the geological period that is most responsible for Assam’s rich oil and coal resources.