Consider the following characteristic features. (a) Closed vascular system (b) External fertilisation (c) Dioecious (d) Double ventral nurve cord The above features characterise

Options

A. Leech
B. Earthworm
C. Sandworm
D. Bloodworm

Answer

To solve the question regarding the characteristic features provided (a) Closed vascular system, (b) External fertilization, (c) Dioecious, and (d) Double ventral nerve cord, we need to analyze each feature and determine which organism they best describe among the options given: leech, earthworm, sandworm, and bloodworm.

### Step-by-Step Solution:

1. **Identify the Features**:
- **Closed Vascular System**: This means that the organism has a circulatory system where blood is contained within vessels.
- **External Fertilization**: This indicates that fertilization occurs outside the body, where gametes meet in the environment.
- **Dioecious**: This means that the organism has distinct male and female individuals.
- **Double Ventral Nerve Cord**: This refers to the presence of two ventral nerve cords running along the length of the organism.

2. **Analyze Each Organism**:
- **Leech**: Leeches have a closed vascular system and can be dioecious, but they typically do not exhibit external fertilization.
- **Earthworm**: Earthworms also have a closed vascular system and are hermaphroditic (not dioecious), and they do not have external fertilization.
- **Sandworm**: Sandworms (or polychaetes) possess a closed vascular system, are dioecious, and exhibit external fertilization. They also have a double ventral nerve cord.
- **Bloodworm**: Bloodworms are similar to sandworms but do not typically exhibit all the features mentioned.

3. **Conclusion**:
Based on the analysis, the organism that best fits all four characteristics (closed vascular system, external fertilization, dioecious, and double ventral nerve cord) is the **sandworm**.

### Final Answer:
The above features characterize the **sandworm**.