Which is the First Eon for Which There is Evidence

Question

Which is the first eon for which there is evidence of life?  
A) Archean eon
B) Proterozoic eon
C) Stromatolite eon
D) Hadean eon
E) Phanerozoic eon

Accepted Answer

The Archean eon, which lasted from 4 to 2.5 billion years ago, is the first eon for which there is evidence of life. Fossil evidence from this period includes stromatolites, which are layered structures formed by microbial communities, as well as microscopic fossils of bacteria-like organisms.