Which two layers are approximately the same age?
core sample 1
core sample 2

Complete question:

Examine the following diagrams. Columns I and II contain rock layers A, B, C, D, E, and F. Both columns were taken from the same dig site at different locations. Which two layers are of approximately the same age? (Note: The diagrams are attached).

C and D  

Explanation:  

Layers C and D apparently contain the same fossilized organisms in the same substrate. Their appearance is very similar. By knowing that certain organisms used to live in a certain period of time, if we find two strata that show the same fossilized organisms, then we can estimate that these two strata are the same age. Fossilized organisms are used to estimate the age of a rocky stratum.

Life history can be illustrated through fossilized organisms trapped or converted into rocks. These fossils are known as index or guide fossils, of animal or vegetal nature, and they can apport information about the rocky stratum in which they are located or incrusted. These fossils are used to determine the age of the rocky sediments or the environmental conditions under which they were deposited.

the answer is:

carbon dioxide

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