Which one is a laevo-rotatory sugar

Options

A. Sucrose
B. Glucose
C. Fructose
D. None of these

Explanation

To determine which sugar is a laevo-rotatory sugar, we need to understand the concept of optical activity and how certain sugars interact with plane polarized light.

### Step-by-Step Solution:

1. **Understanding Optical Activity**:
- Optical activity refers to the ability of a substance to rotate plane polarized light. This is a characteristic of chiral substances, which have non-superimposable mirror images.

2. **Types of Optical Activity**:
- There are two types of optical activity:
- **Dextro-rotatory (d)**: Substances that rotate plane polarized light to the right (clockwise).
- **Laevo-rotatory (l)**: Substances that rotate plane polarized light to the left (counterclockwise).

3. **Identifying the Sugars**:
- The question lists three sugars: glucose, sucrose, and fructose. We need to determine which of these is laevo-rotatory.
- **Glucose**: Dextro-rotatory (rotates light to the right).
- **Sucrose**: Dextro-rotatory (rotates light to the right).
- **Fructose**: Laevo-rotatory (rotates light to the left).

4. **Conclusion**:
- Based on the optical activity of the sugars, fructose is the laevo-rotatory sugar.

### Final Answer:
The laevo-rotatory sugar is **fructose**.

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