Question

In which period did the first mammals appear?
A) Triassic
B) Jurassic
C) Cretaceous
D) Tertiary

Answer 1

Hint: The period between the extinction of the dinosaurs and the present day is called the Age of Mammals or Cenozoic. Mammals appeared on the earth long before the extinction of the dinosaurs.

Complete answer:
Now let's analyze each choice to find the correct answer.
Option A: The first Mammals appeared on earth long before the extinction of dinosaurs. In early years, dinosaurs and mammals existed together in the late Triassic about 200 million years ago. The first mammals appeared in the late Triassic age. So, option A is correct.
Option B: The Jurassic era also known as the age of reptiles which lasted for about 56 million years. During this period, the large reptile also known as dinosaurs existed. So, option B is incorrect.
Option C: The Cretaceous era was the period in which larger continents broke into smaller ones, causing land shift and remodeling the shape and tone of life on earth. During this era, the infamous Tyrannosaurus rex existed as well. No mammals existed during this period. So, option C is incorrect.
Option D: The tertiary (66 million years ago to present) is one of the two periods that exist in the Cenozoic era from 66 million years to 2.6 million years. The second one is called the quaternary period (2.6 million years ago to present). The mammals are more diversified and evolved in this period. So, option D is incorrect.

Thus, the correct answer is option (A) Triassic.

Note: The Late Triassic is the third and final epoch of the Triassic Period in the geologic timescale. The Triassic-Jurassic extinction event began during this and is one of the five major mass extinction events of the Earth. The Age of mammals is known as the Cenozoic era which started from 66 million years ago to present.