The longest phase of meiosis-I is:

Options

A. metaphase I
B. prophase I
C. anaphase I
D. telophase I

Answer

To determine the longest phase of meiosis-I, we can analyze the phases involved in meiosis-I and identify which one is the longest.

### Step-by-Step Solution:

1. **Understanding Meiosis**: Meiosis is a type of cell division that reduces the chromosome number by half, resulting in the formation of gametes (sperms and eggs). It consists of two main stages: meiosis I and meiosis II.

2. **Phases of Meiosis I**: Meiosis I consists of several phases:
- Prophase I
- Metaphase I
- Anaphase I
- Telophase I

3. **Identifying Prophase I**: Among these phases, Prophase I is known to be the most complex and lengthy. It is further divided into five sub-stages:
- **Leptotene**: Chromosomes begin to condense.
- **Zygotene**: Homologous chromosomes pair up (synapsis).
- **Pachytene**: Crossing over occurs, leading to genetic recombination.
- **Diplotene**: Homologous chromosomes begin to separate but remain attached at chiasmata.
- **Diakinesis**: Chromosomes condense further and prepare for metaphase.

4. **Comparing the Length of Phases**: The other phases (Metaphase I, Anaphase I, and Telophase I) are significantly shorter in duration compared to Prophase I.

5. **Conclusion**: Since Prophase I is the longest phase of meiosis I, the correct answer to the question is **Prophase I**.

### Final Answer:
The longest phase of meiosis-I is **Prophase I**.