The body of these animals is circular in cross section. They may be free living ,aquatic and terrestrial . They are bilaterally symmetrical and pseudocoelomate animals. These animals belong to which phylum of animal kingdom?

Options

A. Platyhelminthes
B. Aschelminthes
C. Annelida
D. Arthropoda

Answer

To determine the phylum of the animals described in the question, we can follow these steps:

### Step 1: Analyze the characteristics given in the question.
The question states that the animals have the following characteristics:
- Circular in cross-section
- Free-living (can be aquatic or terrestrial)
- Bilaterally symmetrical
- Pseudocoelomate

### Step 2: Identify the options provided.
The options provided are:
1. Platyhelminthes
2. Aschelminthes
3. Annelida
4. Insecta

### Step 3: Evaluate each option based on the characteristics.
1. **Platyhelminthes**: These are flatworms, which are not circular in cross-section and are acoelomate (lack a coelom). Thus, this option is incorrect.
2. **Aschelminthes**: This group includes roundworms (nematodes) which are indeed circular in cross-section, free-living, and pseudocoelomate. This option matches the characteristics given in the question.
3. **Annelida**: This phylum includes segmented worms like earthworms, which are coelomate (possess a true coelom). Therefore, this option is incorrect.
4. **Insecta**: Insects have jointed appendages and are not characterized by being pseudocoelomate. Thus, this option is also incorrect.

### Step 4: Conclusion
Based on the analysis, the animals described in the question belong to the phylum **Aschelminthes**.

### Final Answer:
The animals belong to the phylum **Aschelminthes**.

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