Question

study the timeline. based on fossil evidence, about how long ago did the first single - celled life form appear on earth? 130 million years ago 1.5 billion years ago 2.5 billion years ago 4.1 billion years ago

Explanation:

Check the timeline for the first single - celled life form. The timeline shows "4.1 BYA Single - celled life". BYA means billion years ago.

Answer:

4.1 billion years ago