the answer is a because if the model is based on experimental data it wont be good unless it has been tested.
Over time, as oxygen levels decrease, CO2 levels increase. Respiration is correct as it uses oxygen as a reactant and releases CO2 as a byproduct.
Proteins are an important class of molecules that carry out most of the work inside cells. The building blocks of proteins are smaller organic molecules called amino acids. Most organisms, including humans, use only 20 different amino acids to assemble the vast multitude of proteins needed to build and run a cell.
To build proteins, cells use a complex assembly of molecules called a ribosome. The ribosome assembles amino acids into the proper order and links them together via peptide bonds. This process, known as translation, creates a long string of amino acids called a polypeptide chain.
After the polypeptide chain is synthesized, it will sometimes undergo additional processing. For example, some proteins will have certain amino acids removed. Or extra molecules such as sugars or phosphates may be attached to some of the amino acids in a protein.
