Which of the following periods is the earliest during which animals may have appeared?

Ordovician period

Cambrian period

Ediacaran period

Cryogenian period

The correct answer is D. Cryogenian period

Explanation

The Cryogenian period (720 million years ago) is known as the period in which the first animals of the earth appeared, which were identified using fossils, these animals were multicellular organisms similar to sponges. Scientists claim that they can be ancestors of modern animals or extinct organisms of which nothing is known and that diversify into multiple forms during the Ediacaran period. So, the correct answer is D. Cryogenian period