Type of fertilization (external or internal) depends on-

Options

A. Structure of egg
B. Site of embryo development
C. Type of sperm
D. 1 and 2 both

Answer

### Step-by-Step Solution

1. **Understanding Fertilization**: Fertilization is the process where male and female gametes unite to form a zygote. The type of fertilization can be categorized as either external or internal.

2. **Identifying Factors Influencing Fertilization**: The type of fertilization depends on several factors, primarily:
- The structure of the egg.
- The site of embryo development.

3. **Examples of External Fertilization**: In aquatic animals such as fish and amphibians, fertilization typically occurs externally. This is because:
- Their eggs are not covered by a protective shell.
- The eggs are released into the water where fertilization occurs outside the female's body.

4. **Examples of Internal Fertilization**: In contrast, terrestrial animals such as reptiles, birds, and mammals usually exhibit internal fertilization. This is because:
- Their eggs are often covered by a protective shell or membrane.
- Fertilization occurs inside the female's body, providing a safer environment for the developing embryo.

5. **Conclusion**: Therefore, the type of fertilization (external or internal) is determined by both the structure of the egg and the site of embryo development. Hence, the correct answer is that it depends on both factors.

### Final Answer
The type of fertilization (external or internal) depends on both the structure of the egg and the site of embryo development.