In porifera, the simplest canal system is

Options

A. ascon type
B. leucon type
C. sycon type
D. radial type

Explanation

To solve the question regarding the simplest canal system in Porifera, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question is asking for the simplest canal system found in the phylum Porifera (sponges).

2. **Identify the Types of Canal Systems**: In Porifera, there are several types of canal systems, namely:
- Ascon type
- Sycon type
- Leucon type
- Cyclone type
- Radial type

3. **Define Each Canal Type**:
- **Ascon Type**: This is the simplest form of canal system where water enters through dermal ostia into a central cavity called the spongocoel and exits through a single opening known as the osculum.
- **Sycon Type**: This is a more complex system where the body wall is folded, allowing for a greater surface area for filtering.
- **Leucon Type**: This is the most complex system, with multiple small chambers and a highly folded body wall, allowing for efficient water flow and filtering.
- **Cyclone Type and Radial Type**: These terms are less commonly used in the classification of canal systems in Porifera and may refer to specific structural adaptations.

4. **Determine the Simplest Type**: Among these types, the Ascon type is recognized as the simplest canal system due to its straightforward structure and direct water flow.

5. **Conclude the Answer**: Therefore, the correct answer to the question is the Ascon type.

### Final Answer:
The simplest canal system in Porifera is the **Ascon type**.

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