Incomplete digestive tract found in -

Options

A. Platyhelminthes and Aschelminthes
B. Platyhelminthes and Ctenophora
C. Aschelminthes and Annelida
D. Coelenterates and Aschelminthes

Answer

To determine which phyla have an incomplete digestive tract, we can analyze the options provided step by step.

### Step-by-Step Solution:

1. **Understanding Incomplete Digestive Tract**:
- An incomplete digestive tract means that the organism has only one opening that serves as both mouth and anus. This is typical in organisms with a gastrovascular cavity.

2. **Analyzing the Options**:
- **Option A: Platyhelminthes and Aschelminthes**:
- Platyhelminthes (flatworms) do have an incomplete digestive tract (gastrovascular cavity).
- Aschelminthes (now often referred to as Ecdysozoa) typically have a complete digestive tract.
- **Conclusion**: This option is partially correct but not fully correct due to Aschelminthes.

3. **Option B: Platyhelminthes and Cnidaria**:
- Platyhelminthes (flatworms) have an incomplete digestive tract.
- Cnidaria (like jellyfish) also have a gastrovascular cavity, which means they also have an incomplete digestive tract.
- **Conclusion**: This option is correct.

4. **Option C: Aschelminthes and Annelida**:
- Aschelminthes generally have a complete digestive tract.
- Annelida (segmented worms) also have a complete digestive tract.
- **Conclusion**: This option is incorrect.

5. **Option D: Cnidaria and Aschelminthes**:
- Cnidaria have an incomplete digestive tract.
- Aschelminthes have a complete digestive tract.
- **Conclusion**: This option is incorrect.

### Final Answer:
The correct answer is **Option B: Platyhelminthes and Cnidaria**, as both phyla have an incomplete digestive tract.