What do scientists estimate is the approximate age of earth ?
a. 660 million years
b. 3.5 billion years
c. 4.6 billion years
d. 12.2 billion years

Scientists discovered fossils in several layers of the earth you see here. they found fossils of algae, snails, and clams in layer d. given that information, where do you think they found fossil evidence of simple land plants and amphibians? a. a b. e c. f d. g