The ______ era is also known as the 'age of mammals'.

Cenozoic

The correct answer is Option 2- Cenozoic

The Cenozoic era is also known as the 'age of mammals'.

The Cenozoic era began 66 million years ago after the extinction of the dinosaurs. During this time, mammals evolved to fill a wide variety of niches on land, in the air, and in the water. Some of the most well-known mammals of the Cenozoic era include horses, elephants, whales, bats, and primates.

The Cenozoic era is divided into two periods: the Tertiary period and the Quaternary period. The Tertiary period lasted from 66 million years ago to 1.8 million years ago. During this time, mammals continued to diversify and become more specialized. The Quaternary period began 1.8 million years ago and continues to the present day. During this time, humans evolved and became the dominant species on Earth.

The Cenozoic era is a time of great change and diversification for mammals. The extinction of the dinosaurs allowed mammals to fill a wide variety of niches and become the dominant land animals on Earth.