In which stage do most cells spend their lives?

Cells primarily spend their lives in interphase, which constitutes the longest phase of the cell cycle. During interphase, the cell is not actively dividing but is instead focused on growth and preparation for division. This phase is comprised of three distinct subphases: G1 (Gap 1), where the cell grows and synthesizes proteins; S (Synthesis), where DNA replication occurs; and G2 (Gap 2), where the cell continues to grow and prepares for mitosis.

Most of a cell's life is spent in interphase because it is crucial for the cell to carry out its normal metabolic activities and to prepare appropriately for the subsequent process of mitosis. The activities during interphase ensure that the cell is adequately equipped with the necessary resources and genetic material to successfully divide and produce two daughter cells.

In contrast, the other stages listed—prophase, metaphase, and anaphase—are all part of the mitotic phase. These stages are relatively short and involve the actual division of the cell. Because interphase encompasses preparation and growth, it is the main stage contributing to the cell's life cycle, making it the correct answer.