Siliceous frustules of diatoms being indestructible, piled up at the bottom of ocean and formed a thick bed over billions of years. Such a thick bed is known as

Options

A. red sea
B. diatomaceous earth
C. pseudorocks
D. red tides.

Explanation

To solve the question regarding the thick bed formed by the indestructible siliceous frustules of diatoms, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Diatoms**:
- Diatoms are a type of algae known for their unique cell walls made of silica. These cell walls are referred to as siliceous frustules.

2. **Formation of Siliceous Frustules**:
- The frustules consist of two overlapping layers: the upper layer is called the apotheca, and the lower layer is called the hypotheca. These layers are made of silica, which is a durable material.

3. **Accumulation Over Time**:
- Over billions of years, the siliceous frustules of diatoms accumulate at the bottom of oceans. Due to their indestructible nature, they do not decompose easily.

4. **Identification of the Thick Bed**:
- The accumulated frustules form a thick bed over time. This specific accumulation of diatom remains is known as diatomaceous earth.

5. **Conclusion**:
- Therefore, the thick bed formed by the piled-up siliceous frustules of diatoms is referred to as **diatomaceous earth**.

### Final Answer:
The thick bed formed by the indestructible siliceous frustules of diatoms is known as **diatomaceous earth**.

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