Cleavage involving in complete division is

Options

A. Spiral
B. Meroblastic
C. Holoblastic
D. Meridional

Answer

**Step-by-Step Solution:**

1. **Understanding Cleavage**: Cleavage refers to the series of rapid cell divisions that occur after fertilization, leading to the formation of a multicellular embryo from a single-celled zygote.

2. **Types of Cleavage**: There are two main types of cleavage:
- **Holoblastic Cleavage**: This is complete cleavage where the entire zygote divides into smaller cells. It occurs in eggs with little to moderate yolk.
- **Meroblastic Cleavage**: This is incomplete cleavage where only a part of the zygote divides, typically occurring in eggs with a large amount of yolk.

3. **Identifying the Question**: The question asks for the type of cleavage that involves incomplete division.

4. **Analyzing the Options**:
- **A. Spiral**: This refers to a pattern of cleavage but does not specifically indicate incomplete division.
- **B. Meroblastic**: This type of cleavage involves incomplete division of the zygote due to the presence of a large yolk.
- **C. Pulloblastic**: This term is not commonly used in the context of cleavage.
- **D. Meridional**: This refers to the orientation of the cleavage plane but does not indicate whether it is complete or incomplete.

5. **Conclusion**: Based on the definitions and characteristics of the types of cleavage, the correct answer is **B. Meroblastic**, as it specifically refers to cleavage involving incomplete division.

**Final Answer**: B. Meroblastic

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