The correct option is C Electron transport system
Amphibolic pathways are pathways that are catabolic and anabolic in nature, that is, they bring about breakdown of biomolecules to generate energy and they create intermediate molecules that can be channelled into different biosynthesis pathways. Kreb's cycle, glycolytic pathway are all examples of amphibolic pathways, because they generate net ATPs and also build up many intermediate biomolecules that are used up for synthesis of aminoacids, carbohydrates, fats etc. The only pathway given here that is not amphibolic is the Electron transport system (ETS). The ETS is purely catabolic in nature, as it causes the production of ATP through oxidative phosphorylation and the byproducts produced are water and carbon dioxide that can not be used for production of any biomolecules.