The primary producers of the deep-sea hydrothermal vent ecosystem are:

Options

A. Green algae
B. Chemosynthetic bacteria
C. blue-green algae
D. coral reefs

Explanation

**Step-by-Step Solution:**

1. **Understanding the Ecosystem**: The question asks about the primary producers in the deep-sea hydrothermal vent ecosystem. Hydrothermal vents are located deep in the ocean, where sunlight does not penetrate.

2. **Identifying Primary Producers**: Primary producers are organisms that can produce their own food. In most ecosystems, this is typically done through photosynthesis, which requires sunlight.

3. **Considering the Environment**: Since hydrothermal vents are located in deep-sea environments where sunlight cannot reach, traditional photosynthetic organisms (like plants and algae) cannot thrive there.

4. **Evaluating Options**:
- Green algae and blue-green algae are both photosynthetic organisms that require sunlight, so they cannot be the primary producers in this environment.
- Coral is also dependent on sunlight for photosynthesis and thus is not suitable for deep-sea conditions.

5. **Identifying the Correct Organisms**: The primary producers in hydrothermal vent ecosystems are not reliant on sunlight. Instead, they utilize chemosynthesis, a process where certain bacteria convert chemical energy from inorganic molecules (like hydrogen sulfide) into organic matter.

6. **Conclusion**: Therefore, the primary producers of the deep-sea hydrothermal vent ecosystem are chemosynthetic bacteria.

**Final Answer**: Chemosynthetic bacteria.

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