what stage of cellular respiration does not involve any carbon-based compounds as a reactant or product?

electron transport chain
krebs cycle
glycolysis
fermentation

The correct answer is "Electron transport chain".

Explanation:

An electron transport chain (ETC) refers to a series of reduction and oxidation (redox) reactions that take place among compounds that serve as electron donors and electron acceptors. In cellular respiration, ETC takes place along the membrane with oxygen serving as the final electron acceptor and a series of intermediates that carry the electrons towards the oxygen. Since ETC involves redox reactions occurring among intermediates, this stage of cellular respiration does not involve any carbon-based compounds as a reactant or product.

the correct answer is phenotype