Cellular metabolism is the process of breakdown of nutrients to produce energy; this also includes various chemical reactions in a series of metabolic pathways (glycolysis, citric acid cycle, beta-oxidation etc) that are taking place in the cell.
The energy produced may be utilised to carryout regular activities of the cell (catabolism), or to build new organic molecules (anabolism).
Thus, the options (b), (c) and (d) are incorrect.
Cellular metabolism is the process of breakdown of nutrients to produce energy; this also includes various chemical reactions in a series of metabolic pathways (glycolysis, citric acid cycle, beta-oxidation etc) that are taking place in the cell.
Therefore, the correct option is – A. Metabolic pathways.