Pentoses and hexoses are the most common
Or
The simple polyhydroxy ketone molecule containing 3-7 carbons is a

Options

A. Disaccharides
B. Monosaccharides
C. Oligosaccharides
D. Polysaccharides

Explanation

To solve the question regarding pentoses and hexoses, we need to break down the information provided step by step.

### Step-by-Step Solution:

1. **Understanding Pentoses and Hexoses**:
- Pentoses are monosaccharides that contain **5 carbon atoms**.
- Hexoses are monosaccharides that contain **6 carbon atoms**.
- Both pentoses and hexoses are types of simple sugars.

2. **Identifying the Type of Molecule**:
- The question mentions a "simple polyhydroxy ketone molecule" that contains **3 to 7 carbon atoms**.
- This description fits the definition of monosaccharides, which are the simplest form of carbohydrates.

3. **Defining Monosaccharides**:
- Monosaccharides are classified based on the number of carbon atoms they contain:
- **Triose**: 3 carbon atoms
- **Tetrose**: 4 carbon atoms
- **Pentose**: 5 carbon atoms
- **Hexose**: 6 carbon atoms
- **Heptose**: 7 carbon atoms

4. **Conclusion**:
- Since both pentoses and hexoses fall under the category of monosaccharides, we can conclude that they are indeed the most common types of monosaccharides.
- Therefore, the correct answer to the question is that pentoses and hexoses are the most common **monosaccharides**.

### Final Answer:
**Pentoses and hexoses are the most common monosaccharides.**

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