Which of the following is not a chemically modified sugar ?

Options

A. Glucosamine
B. N-acetyl galactosamine
C. Galacturonic acid
D. Dihydroxy acetone

Answer

To determine which of the following options is not a chemically modified sugar, we will analyze each option provided:

1. **Glucosamine**: This is an amino sugar derived from glucose by the addition of an amino group. It is a chemically modified form of sugar.

2. **Acetyl Galactosamine**: Similar to glucosamine, acetyl galactosamine is also an amino sugar. It is derived from galactose through biochemical modifications, making it a chemically modified sugar.

3. **Galacturonic Acid**: This is a sugar acid that is derived from galactose through oxidation. It is also considered a chemically modified sugar.

4. **Dihydroxyacetone**: This is a simple sugar (triose) that is not chemically modified. It is a naturally occurring carbohydrate that is not derived from any modification of another sugar.

Based on this analysis, the answer to the question is:

**Dihydroxyacetone is not a chemically modified sugar.**

### Step-by-Step Solution:
1. Identify each option and its chemical nature.
2. Determine if each sugar is a modified form of another sugar.
3. Conclude which option is not a chemically modified sugar.