Answer:
the upper layer of the Earth's mantle
Explanation:
Not the ocean, impossible to be in top of the core, not in the air
RNA contains the genetic code
<em><u>Answer</u></em>
<em><u>about 3.9 billion years ago</u></em>
<em><u>about 3.9 billion years agoThe most recent common ancestor of all currently living organisms is the last universal ancestor, which lived about 3.9 billion years ago.</u></em>
