Which of the following monosaccharides is a pentose?

Options

A. Glucose
B. Fructose
C. Arabinose
D. Galactose

Answer

To determine which of the following monosaccharides is a pentose, we need to analyze the number of carbon atoms in each option provided. A pentose is defined as a monosaccharide that contains five carbon atoms.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are glucose, fructose, arabinose, and galactose.

2. **Count the Carbon Atoms in Each Monosaccharide**:
- **Glucose**: Glucose has 6 carbon atoms (C6H12O6).
- **Fructose**: Fructose also has 6 carbon atoms (C6H12O6).
- **Arabinose**: Arabinose has 5 carbon atoms (C5H10O5).
- **Galactose**: Galactose has 6 carbon atoms (C6H12O6).

3. **Determine Which is a Pentose**:
- From the analysis, we see that glucose, fructose, and galactose all have 6 carbon atoms, while arabinose has 5 carbon atoms.

4. **Conclusion**: Since arabinose is the only monosaccharide with 5 carbon atoms, it is classified as a pentose.

### Final Answer:
The monosaccharide that is a pentose among the options is **arabinose**.

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