Choose the option which describes the Aschelminthes with its exclusive features

Answer

To solve the question regarding the exclusive features of Aschelminthes (also known as Nematodes or roundworms), we can break down the solution into the following steps:

### Step 1: Identify the Body Structure
- Aschelminthes are characterized by an **unsegmented body**. This means that their body does not have the segmented structure seen in other phyla like Annelida.
- **Hint**: Remember that segmentation refers to the division of the body into repetitive segments, which is not a feature of Aschelminthes.

### Step 2: Examine the Muscular Pharynx
- Aschelminthes possess a **muscular pharynx** which is adapted for feeding. This structure helps them in the ingestion of food.
- **Hint**: The muscular pharynx is a key feature that aids in their feeding mechanism, distinguishing them from other groups.

### Step 3: Understand the Body Cavity
- Aschelminthes have a **pseudocoelom**. This means they have a body cavity that is not completely lined with mesoderm. It is a fluid-filled space that lies between the gut and the body wall.
- **Hint**: The term "pseudocoelom" indicates that the body cavity is not a true coelom, which is a characteristic feature of this phylum.

### Step 4: Sexual Dimorphism
- In Aschelminthes, there is a notable **sexual dimorphism** where the **female is generally longer than the male**. This is a unique characteristic that can help in identifying them.
- **Hint**: Look for differences in size between males and females in many species, as this is a common trait in Aschelminthes.

### Step 5: Conclusion
- Based on the above features, the correct option that describes Aschelminthes includes:
- Unsegmented body
- Muscular pharynx
- Pseudocoelom
- Female longer than male

Thus, the correct answer is **Option 1**.