Well-developed alimentary canals and muscular pharynxes are present in:

Options

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

Answer

To solve the question regarding which organism has well-developed alimentary canals and muscular pharynxes, we can follow these steps:

### Step 1: Understand the Terms
- **Alimentary Canal**: This is a continuous tube that runs from the mouth to the anus, allowing for the digestion and absorption of food.
- **Muscular Pharynx**: This is a muscular part of the digestive system that helps in swallowing food.

### Step 2: Analyze the Options
- **Platyhelminthes**: These are flatworms, which typically do not have a well-developed alimentary canal. They often have a gastrovascular cavity instead.
- **Aschelminthes**: This group includes organisms with a pseudocoelom, which allows for a more complex digestive system, including a well-developed alimentary canal and muscular pharynx.
- **Annelida**: These are segmented worms that also have a well-developed digestive system, but the question specifically asks for the presence of muscular pharynxes.
- **Arthropoda**: This group includes insects and other arthropods. They have a complex digestive system, but they do not have a muscular pharynx in the same sense as Aschelminthes.

### Step 3: Evaluate Each Option
- **Platyhelminthes**: Not applicable due to lack of a well-developed alimentary canal.
- **Aschelminthes**: Correct choice as they possess both a well-developed alimentary canal and muscular pharynx.
- **Annelida**: While they have a developed digestive system, they do not fit the criteria as well as Aschelminthes.
- **Arthropoda**: Incorrect due to the absence of a muscular pharynx.

### Step 4: Conclusion
Based on the analysis, the organism that has well-developed alimentary canals and muscular pharynxes is **Aschelminthes**.

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