Preparation of cell differentiation are completed in-

Options

A. Morula
B. Blastula
C. Gastrula
D. Neurula

Answer

To answer the question regarding when the preparation of cell differentiation is completed, we can break down the process step by step:

### Step-by-Step Solution:

1. **Fertilization and Zygote Formation**: The process begins with fertilization, leading to the formation of a zygote. This zygote is a single cell that will undergo several divisions.

2. **Cleavage and Morula Formation**: The zygote undergoes a series of mitotic divisions known as cleavage. After several rounds of cleavage, a 16-cell structure called the morula is formed.

3. **Blastula Formation**: The morula continues to divide, resulting in a structure known as the blastula, which typically consists of 32 to 128 cells. The cells in the blastula are still not differentiated.

4. **Differentiation Begins**: Within the blastula, the cells start to undergo differentiation. This is the preparation phase for cell differentiation, where the cells begin to specialize and form different types of tissues.

5. **Gastrula Formation**: As differentiation progresses, the blastula transforms into the gastrula. The gastrula is characterized by the formation of three germ layers: ectoderm, mesoderm, and endoderm. This stage indicates that differentiation has occurred, and the cells are now organized into distinct layers.

6. **Conclusion**: The preparation for cell differentiation is completed in the blastula stage, as this is where the cells begin to organize and prepare for further specialization, leading to the formation of the gastrula.

### Final Answer:
The preparation of cell differentiation is completed in the **Blastula**.