Scientists can determine if oxygen existed in earth's archean atmosphere by a. determining the amount of outgassing that occurred. b. looking for oxidized iron in rocks. c. looking at the amount of salt content in rocks. d. determining how many people survived

Answer;

B. looking for oxidized iron in rocks.

Explanation;

-Scientists believe that the Archean atmosphere had been free of free oxygen. They believed that banded iron formations did not occur till near the end of the Archean period.

-The oxygen that was being produced by cyanobacteria was only enough for the weathering process. There was only enough oxygen that remained in the atmosphere when the rocks at the surface were properly and adequately oxidized. Therefore, by looking for oxidized iron in rocks scientists were able to determine if oxygen existed in Earth's Archean atmosphere.

i think the answer would be d

a physical change is being made.