Metabolism means

The correct option is expansion of cell.

Metabolism encompasses all the biochemical reactions that occur within a living organism to sustain life. These reactions are responsible for generating energy and synthesizing the essential building blocks (such as proteins, lipids, and nucleic acids) required by the cell.
As these metabolic processes proceed, the cell accumulates these newly synthesized materials, leading to an increase in cellular volume and physical growth. Therefore, the expansion of a cell is a direct physiological consequence of its active metabolic processes.