Read the following statements :
(a) Over one - third of all named species on earth are arthropods.
(b) All mollusuc contain a file like a rasping organ for feeding.
(c ) Nereis possess parapoida which help in swimming.
(d) Development is indirect in Bufo.
Choose the incorrect statements.

Options

A. (a) and (b) only
B. (b) and (c ) only
C. (c ) and (d) only
D. None of these

Answer

To solve the question, we need to evaluate each statement one by one and identify the incorrect ones.

### Step-by-Step Solution:

1. **Evaluate Statement (a)**:
- The statement claims that "over one-third of all named species on earth are arthropods."
- Arthropods are indeed one of the largest phyla in the animal kingdom, comprising a significant portion of all known species. However, it is estimated that arthropods make up more than two-thirds (around 60-70%) of all named species, which means this statement is incorrect as it underestimates their proportion.

**Hint**: Consider the estimated proportion of arthropods in relation to all named species.

2. **Evaluate Statement (b)**:
- The statement asserts that "all mollusks contain a file-like rasping organ for feeding."
- While many mollusks possess a radula (the rasping organ), it is not present in all classes of mollusks. For example, bivalves (like clams and oysters) do not have a radula. Therefore, this statement is also incorrect.

**Hint**: Think about the different classes within the phylum Mollusca and their characteristics.

3. **Evaluate Statement (c)**:
- The statement states that "Nereis possess parapodia which help in swimming."
- Nereis, a genus of polychaete worms, indeed has parapodia, which are lateral appendages that assist in locomotion, including swimming. This statement is correct.

**Hint**: Recall the anatomy of Nereis and its adaptations for movement.

4. **Evaluate Statement (d)**:
- The statement claims that "development is indirect in Bufo."
- Bufo is a genus of toads, and like many amphibians, they undergo indirect development, which includes a larval stage (tadpole). This statement is correct.

**Hint**: Consider the life cycle of amphibians and the presence of larval stages.

### Conclusion:
After evaluating all the statements, we find that statements (a) and (b) are incorrect. Therefore, the answer to the question is that the incorrect statements are (a) and (b).

### Final Answer:
**Incorrect Statements**: (a) and (b)