What is true of bacillariophyceae

Options

A. Epitheca is smaller
B. Hypotheca is smaller
C. Both epitheca and hypotheca have same size
D. Any of the two can be larger.

Answer

### Step-by-Step Solution:

1. **Understanding Bacillariophyceae**: Bacillariophyceae, commonly known as diatoms, are a group of unicellular algae characterized by their unique cell wall structure.

2. **Structure of Diatoms**: The cell wall of diatoms is made up of silica and is referred to as a frustule. This frustule is composed of two parts: the epitheca and the hypotheca.

3. **Defining Epitheca and Hypotheca**:
- **Epitheca**: This is the larger, upper part of the frustule.
- **Hypotheca**: This is the smaller, lower part of the frustule.

4. **Comparing Sizes**: In diatoms, the epitheca is always larger than the hypotheca. Therefore, the statement that the hypotheca is smaller is true.

5. **Evaluating the Options**:
- Option 1: Epitheca is smaller - **False**
- Option 2: Hypotheca is smaller - **True**
- Option 3: Both epitheca and hypotheca are the same size - **False**
- Option 4: Any of the two can be larger - **False**

6. **Conclusion**: The correct statement about Bacillariophyceae is that the hypotheca is smaller than the epitheca.

### Final Answer:
The correct option is: **Hypotheca is smaller.**

---