In Earthworm, both sexes are present and they undergo :

Options

A. Cross fertilization
B. Asexual reproduction
C. Self fertilization
D. Both (1) and (3)

Answer

### Step-by-Step Solution:

1. **Understanding Earthworm Reproduction**:
- Earthworms are hermaphrodites, meaning they possess both male and female reproductive organs. This allows them to produce both eggs and sperm.

2. **Process of Copulation**:
- During copulation, two earthworms align themselves ventrally. One earthworm transfers its sperm to the spermathecae (sperm storage) of the other earthworm.

3. **Formation of Cocoon**:
- After copulation, the earthworms secrete a mucous cocoon from the clitellum (a thickened, glandular section of the body). This cocoon contains the eggs and the stored sperm.

4. **Fertilization**:
- Fertilization occurs within the cocoon. The sperm from one earthworm fertilizes the eggs of the other, resulting in the formation of zygotes.

5. **Conclusion**:
- Since earthworms undergo copulation and fertilization with another individual, they primarily reproduce through cross-fertilization.

6. **Elimination of Other Options**:
- Asexual reproduction is not applicable here as earthworms do not reproduce without the involvement of both sexes.
- Self-fertilization is also incorrect because, despite being hermaphrodites, earthworms engage in cross-fertilization rather than fertilizing their own eggs.

### Final Answer:
- The correct answer is **cross fertilization**.

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