Question

fossils were left by species that lived over a relatively brief span of time, making them useful for the choose... of rock layers. to determine the absolute age of fossils, scientists can use choose... by applying the known choose... of an isotope.

Answer 1

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the answer to the question is:

index fossils were left by species that lived over a relatively brief span of time, making them useful for the __(relative dating)__ of rock layers. to determine the absolute age of fossils, scientists can use __(radiometric dating)__ by applying the known __(half-life)__ of an isotope.