Earth probably formed _____ years ago, and the first life evolved as early as _____ years ago.Hint: Because fossils of bacterial communities have been discovered that are 3.5 billion years old, it is reasonable to assume life originated around 3.9 billion years ago.
a. 3.9 million years ago ... 2.0 billion years ago
b. 10 billion years ago ... 4.5 billion years ago
c. 4.5 billion years ago ... 3.9 billion years ago
d. 6,000 years ago ... 6,000 years ago
e. humans observed neither event, so there is no way to tell.