Reducing sugars are

Options

A. Glucose , fructose, maltose , galactose and lactose
B. Glucose, sucrose and cellulose
C. Lactose , starch, glycogen and trehalose
D. All of the above

Answer

### Step-by-Step Solution:

1. **Understanding Sugars**:
- Sugars can be classified into two main categories: reducing sugars and non-reducing sugars.

2. **Defining Reducing Sugars**:
- Reducing sugars are those that have a free aldehyde or ketone group, which allows them to act as reducing agents. This property is primarily due to the presence of a hydroxyl (OH) group attached to the anomeric carbon.

3. **Identifying the Anomeric Carbon**:
- The anomeric carbon is the carbon atom in a sugar that is bonded to two oxygen atoms: one in a hydroxyl group and the other in a ring structure. If this carbon has an OH group, the sugar is classified as a reducing sugar.

4. **Examples of Reducing Sugars**:
- Common reducing sugars include monosaccharides like glucose, fructose, galactose, and disaccharides like lactose and maltose. All of these sugars can reduce other compounds due to the presence of the anomeric carbon with an OH group.

5. **Identifying Non-Reducing Sugars**:
- Non-reducing sugars, such as sucrose and cellulose, do not have a free aldehyde or ketone group because their anomeric carbons are involved in glycosidic bonds and do not have an OH group available for reduction.

6. **Conclusion**:
- Based on the classification, glucose, fructose, maltose, galactose, and lactose are all reducing sugars. Therefore, the correct answer to the question is that all these sugars are reducing sugars.