Cytokinesis:

Options

A. is half a chromosome
B. is the longest part of the cell cycle
C. is mitosis in plants
D. requires the formation of a cell plate in plant cells

Answer

### Step-by-Step Solution for the Question on Cytokinesis:

1. **Understanding Cytokinesis**: Cytokinesis is the process that occurs after the M phase of the cell cycle, specifically after mitosis (karyokinesis). It involves the division of the cytoplasm, resulting in two separate daughter cells.

2. **Identifying the Context**: In the context of plant cells, after mitosis, the cell contains two nuclei. The next step is to divide the cytoplasm to form two distinct cells.

3. **Formation of the Cell Plate**: In plant cells, cytokinesis is characterized by the formation of a structure known as the cell plate. This structure forms in the middle of the cell and is crucial for dividing the cytoplasm.

4. **Completion of Cytokinesis**: Once the cell plate is fully formed, it develops into the new cell wall that separates the two daughter cells, thus completing the process of cytokinesis.

5. **Evaluating the Options**:
- **Option A (Half a chromosome)**: This does not relate to cytokinesis.
- **Option B (The longest part of the cell cycle)**: This is incorrect as cytokinesis is not the longest phase.
- **Option C (Mitosis in plants)**: This is misleading; cytokinesis is distinct from mitosis.
- **Option D (Requires the formation of a cell plate in plant cells)**: This is correct as it accurately describes the process of cytokinesis in plant cells.

6. **Conclusion**: The correct answer to the question about cytokinesis is **Option D**.