The correct answer is A. Hadean Eon
Step-by-step explanation:
The Hadean Eon is the earliest Eon registered in the geological scale and the first eon in the Precambrian, this eon began 4.6 billion years ago and ended 4 billion years ago. It was during this Eon the Solar System was in formation and also during this, the Earth formed as well as basic elements that were later necessary for the emergence of life including the development of the atmosphere and oceans, although during the Hadean Eon the conditions in Earth were mainly unstable, this is the reason this Eon is called Hadean that refers to the Greek god Hades related to hell as the conditions on Earth were "hellish".