Which of the following fundamental feature is common to Balanoglossus, anopheles and laccifer without any exception?

Options

A. Marine habitat
B. Members of largest phylum of animal kingdom
C. Open circulatory system
D. External fertilisation

Explanation

To determine which fundamental feature is common to Balanoglossus, Anopheles, and Laccifer without any exception, we will analyze each option provided in the question.

### Step 1: Identify the organisms and their classifications
- **Balanoglossus**: This organism belongs to the phylum Hemichordata.
- **Anopheles**: This is a genus of mosquitoes that belong to the phylum Arthropoda.
- **Laccifer**: This is also an insect and belongs to the phylum Arthropoda.

### Step 2: Analyze each option
1. **Marine habitat**:
- Balanoglossus is a marine organism, but Anopheles and Laccifer are terrestrial. Therefore, this feature is not common to all three.

2. **Member of the largest phylum of the animal kingdom**:
- The largest phylum is Arthropoda, which includes Anopheles and Laccifer. However, Balanoglossus belongs to Hemichordata, so this feature is also not common to all three.

3. **Open circulatory system**:
- Both Arthropoda (Anopheles and Laccifer) and Hemichordata (Balanoglossus) have an open circulatory system. This feature is common to all three organisms.

4. **External fertilization**:
- While many organisms in these groups may exhibit external fertilization, some may also have internal fertilization. Therefore, this feature is not universally applicable to all three.

### Step 3: Conclusion
Based on the analysis, the only fundamental feature that is common to Balanoglossus, Anopheles, and Laccifer without any exception is the **open circulatory system**.

### Final Answer
The correct answer is: **Open circulatory system**.

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