Bivalved siliceous shell or frustule occurs in

Options

A. Diatoms
B. Foraminiferans
C. Radiolarians
D. Heliozoans.

Answer

To answer the question about which organism has a bivalved siliceous shell or frustule, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Term "Bivalved Siliceous Shell"**:
- The term "bivalved" refers to a structure that consists of two halves or valves.
- "Siliceous" indicates that the shell is made of silica (silicon dioxide).

2. **Identifying the Options**:
- The options provided are:
- A) Diatoms
- B) Foraminiferans
- C) Radiolarians
- D) Halusones

3. **Analyzing Each Option**:
- **Option A: Diatoms**:
- Diatoms are unicellular algae that have a cell wall made of silica. This cell wall is known as a frustule and is indeed bivalved.
- **Option B: Foraminiferans**:
- Foraminiferans have a shell made of calcium carbonate, not silica.
- **Option C: Radiolarians**:
- Radiolarians possess a shell made of silica, but it is not specifically bivalved like that of diatoms.
- **Option D: Halusones**:
- Halusones have a shell composed of silica and organic material, but again, it is not specifically bivalved.

4. **Conclusion**:
- Based on the analysis, the organism that has a bivalved siliceous shell or frustule is **Option A: Diatoms**.

### Final Answer:
The bivalved siliceous shell or frustule occurs in **Diatoms**.

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