Which of the following statements are correct?
(A) Tapeworms are hermaphrodites and undergo self fertilisation.
(B) Earthworms are hermaphrodites and undergo self fertilisation.
(C) Tapeworms are hermaphrodites but undergo cross fertilisation.
(D) Earthworms are hermaphrodites but undergo cross fertilisation.

Options

A. 'A' and 'B' only
B. A' and 'D' only
C. 'B' and 'C' only
D. 'C' and 'D' only

Explanation

To solve the question regarding the correctness of the statements about tapeworms and earthworms, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Analyze Statement (A)**: "Tapeworms are hermaphrodites and undergo self-fertilization."
- **Explanation**: Tapeworms possess both male and female reproductive organs in each segment. They can indeed undergo self-fertilization, meaning that the male and female gametes come from the same organism.
- **Conclusion**: This statement is **correct**.

2. **Analyze Statement (B)**: "Earthworms are hermaphrodites and undergo self-fertilization."
- **Explanation**: Earthworms are also hermaphrodites, but they typically do not self-fertilize. Instead, they engage in cross-fertilization, where two earthworms exchange sperm.
- **Conclusion**: This statement is **incorrect**.

3. **Analyze Statement (C)**: "Tapeworms are hermaphrodites but undergo cross-fertilization."
- **Explanation**: While tapeworms are hermaphrodites, they primarily undergo self-fertilization rather than cross-fertilization.
- **Conclusion**: This statement is **incorrect**.

4. **Analyze Statement (D)**: "Earthworms are hermaphrodites but undergo cross-fertilization."
- **Explanation**: As mentioned earlier, earthworms are hermaphrodites and they do undergo cross-fertilization by exchanging gametes with another earthworm.
- **Conclusion**: This statement is **correct**.

### Final Evaluation:
- The correct statements are (A) and (D).
- Therefore, the correct option is **A and D only**.