In animal cytokinesis, cleavage occurs with the help of

Options

A. Microtubules
B. Spindle fibres
C. Microfibrils
D. Microfilaments

Answer

### Step-by-Step Text Solution:

1. **Understanding Cytokinesis**:
- Cytokinesis is the process that occurs at the end of cell division, where the cytoplasm of a parental cell is divided into two daughter cells.

2. **Cytokinesis in Animal Cells**:
- In animal cells, cytokinesis is characterized by the formation of a cleavage furrow. This is a key feature that distinguishes animal cell division from that of plant cells, which form a cell plate.

3. **Formation of the Cleavage Furrow**:
- The cleavage furrow is formed by a structure known as the contractile ring. This ring is crucial for the physical separation of the two daughter cells.

4. **Role of Contractile Proteins**:
- The contractile ring is primarily composed of contractile proteins, specifically actin and myosin filaments. These proteins are essential for the contraction that leads to the deepening of the cleavage furrow.

5. **Microfilaments**:
- The contractile ring is initiated and supported by microfilaments, which are part of the cytoskeleton. These microfilaments play a vital role in the contraction process during cytokinesis.

6. **Excluding Other Options**:
- Microtubules and spindle fibers are involved in mitosis (karyokinesis) but do not play a role in cytokinesis. Microfibrils are also not involved in this process. Therefore, they can be ruled out as options.

7. **Conclusion**:
- The correct answer to the question is that in animal cytokinesis, cleavage occurs with the help of **microfilaments**.