B.) Sodium is in the left than any other...so it's the most metallic
It becomes inactive in the stomach because of the stomach having a MUCH greater PH level then the mouth. It is typically 1.0-2.0 in the Stomach which is extremely acidic which causes it to change shape and therefore inactive.
The fossils that provide information on the formation of an oxygen-rich atmosphere are the stromatilites from the Precambrian era. These are layered and columnar fossils consisting mainly of cyanobacteria which were the original life form back then. These bacteria took in carbon dioxide and produced oxygen by photosynthesis as early as 2.5 billion years ago (the earth is about 4.5 billion yrs old).
