The following process occurs in metaphase :
(a) centrioles move to opposite poles
(b) chromosomes line up along the equator of the dividing cell
(c) chromosomes move to opposite poles
(d) nuclear envelope disappears

Options

A. centrioles move to opposite poles
B. chromosomes line up along the equator of the dividing cell
C. chromosomes move to opposite poles
D. nuclear envelope disappears

Answer

To determine which process occurs during metaphase, we need to analyze each option in the context of the cell cycle, specifically focusing on the events that take place during metaphase.

### Step-by-Step Solution:

1. **Understanding the Cell Cycle Phases**:
- The cell cycle consists of several phases: Interphase (G1, S, G2) and M phase (mitosis and cytokinesis).
- Mitosis is further divided into four main stages: prophase, metaphase, anaphase, and telophase.

2. **Identifying Events in Each Phase**:
- **Prophase**: The nuclear envelope begins to break down, and chromosomes condense and become visible. Centrioles move to opposite poles.
- **Metaphase**: Chromosomes align along the equatorial plane (the metaphase plate) of the cell. This is a critical step for ensuring that each daughter cell will receive an identical set of chromosomes.
- **Anaphase**: The sister chromatids are pulled apart and move toward opposite poles of the cell.
- **Telophase**: The nuclear envelope re-forms around each set of chromosomes, which begin to de-condense.

3. **Analyzing Each Option**:
- **(a) Centrioles move to opposite poles**: This occurs during prophase, not metaphase.
- **(b) Chromosomes line up along the equator of the dividing cell**: This is the defining characteristic of metaphase.
- **(c) Chromosomes move to opposite poles**: This occurs during anaphase, not metaphase.
- **(d) Nuclear envelope disappears**: This happens during prophase, not metaphase.

4. **Conclusion**:
- The correct answer is **(b) chromosomes line up along the equator of the dividing cell**, as this is the key event that occurs during metaphase.

### Final Answer:
The process that occurs in metaphase is **(b) chromosomes line up along the equator of the dividing cell**.