Question

One of the following period witnessed the extinction of dinosaurs and primitive birds.

• A. Cretaceous
• B. Jurassic
• C. Pleistocene
• D. Triassic

Answer 1

Answer: (A)

Cretaceous

• The earth contains different layers of sediments, of which the bottom layer is the oldest layer and the upper layer is the most recent layer. Based on the age of rocks, a time scale was prepared and it is called the geological time scale, it depicts the different stages of the evolution of life on the earth over the past millions of years.
• It consists of three Eons, that consists of Eras which are divided into Periods that may be further subdivided into Epochs. These Eras, Periods, Epochs depict the time of origin and the dominance of the certain group of animals during certain Eras or Periods. It provides the most direct evidence for the concept of evolution.
  
• In order from oldest to youngest, the three Eons are as follows

Archean Eon: ancient or archaic (oldest rocks on earth)

Proterozoic Eon: beginning life (2.5 billion to 542 million years ago)

Phanerozoic Eon: visible life (542 million years ago to present)

• The Cretaceous period witnessed the extinction of dinosaurs and primitive birds. First modern birds appeared Primitive placental mammals as insectivorous shrews originated.

So, the correct option is 'Cretaceous'.