Yolk plug can be seen during which developmental process of frog?

Options

A. Gastrulation
B. Blastulation
C. Cleavage
D. Organogenesis

Answer

### Step-by-Step Solution:

1. **Understanding the Yolk Plug**: The yolk plug is a portion of the embryo that provides nutrients to the developing frog. It is crucial for the growth of the embryo during early development.

2. **Identifying Developmental Stages**: Frog development consists of several stages: cleavage, blastulation, gastrulation, and organogenesis. Each stage has distinct characteristics and functions.

3. **Cleavage Stage**: This is the initial stage where the zygote divides into smaller cells (2-cell, 4-cell, 8-cell stages). During this stage, the yolk plug is not formed.

4. **Blastulation Stage**: In this stage, the embryo forms a structure called the blastula, which contains around 100 cells. The blastula has a fluid-filled cavity called the blastocoel. The yolk plug is also not present during this stage.

5. **Gastrulation Stage**: This is the critical stage where the yolk plug is formed. It occurs when the number of cells reaches around 1000 or more. During gastrulation, the cells begin to migrate and differentiate, and the yolk plug serves as a nutrient source for the developing embryo.

6. **Organogenesis Stage**: This is the stage where the organs start to form and tissues develop further. The yolk plug is not significant in this stage as the focus shifts to organ development.

7. **Conclusion**: The yolk plug is specifically observed during the gastrulation phase of frog development.

### Final Answer:
The yolk plug can be seen during the **gastrulation** phase of frog development.

---