Which of the following is longest phase of the cell cycle?

Options

A. Prophase
B. Interphase
C. Telophase
D. M-phase

Answer

To determine which phase of the cell cycle is the longest, we can analyze the options provided:

1. **Prophase**: This phase is part of mitosis (or meiosis) where the chromatin condenses into chromosomes. While prophase can be lengthy compared to other stages of mitosis, it is not the longest phase of the entire cell cycle.

2. **Interphase**: This is the longest phase of the cell cycle. Interphase consists of three sub-phases: G1 (cell growth), S (DNA synthesis), and G2 (preparation for mitosis). During interphase, the cell grows, duplicates its DNA, and prepares for division, making it significantly longer than the phases of mitosis.

3. **Telophase**: This is another phase of mitosis where the nuclear membrane reappears and the cell prepares to divide into two daughter cells. Similar to prophase, telophase is not the longest phase of the entire cell cycle.

4. **M phase**: This phase includes both mitosis and cytokinesis, where the cell divides. While this phase is crucial, it is relatively short compared to interphase.

Based on this analysis, the longest phase of the cell cycle is **Interphase**.

### Final Answer:
The longest phase of the cell cycle is **Interphase**.