To determine which set of carbohydrates contains reducing sugars, we need to first understand what a reducing sugar is. Reducing sugars are carbohydrates that can donate electrons to another chemical, which means they can reduce other substances. This property is typically identified through tests such as the Tollens' test and the Fehling's test.
### Step-by-step Solution:
1. **Definition of Reducing Sugars**:
- Reducing sugars are carbohydrates that have a free aldehyde group (-CHO) or a free hemiacetal group. They can reduce Tollens' reagent (producing a silver mirror) and Fehling's reagent (producing a red precipitate of copper(I) oxide).
2. **Identify Common Reducing Sugars**:
- Common reducing sugars include:
- **Glucose**: Contains an aldehyde group.
- **Fructose**: Although it is a ketose, it can convert to an aldehyde form through tautomerization, making it a reducing sugar.
- **Lactose**: Contains a hemiacetal group, making it a reducing sugar.
- **Maltose**: Contains a hemiacetal group, making it a reducing sugar.
- **Sucrose**: Is a non-reducing sugar because it does not have a free aldehyde or hemiacetal group.
3. **Evaluate Each Option**:
- **Option A: Glucose, Fructose, Sucrose**:
- Glucose (reducing), Fructose (reducing), Sucrose (non-reducing).
- This option is incorrect due to the presence of sucrose.
- **Option B: Sucrose, Lactose, Glucose**:
- Sucrose (non-reducing), Lactose (reducing), Glucose (reducing).
- This option is incorrect due to the presence of sucrose.
- **Option C: Sucrose, Maltose, Fructose**:
- Sucrose (non-reducing), Maltose (reducing), Fructose (reducing).
- This option is incorrect due to the presence of sucrose.
- **Option D: Maltose, Lactose, Fructose**:
- Maltose (reducing), Lactose (reducing), Fructose (reducing).
- This option is correct as all are reducing sugars.
4. **Conclusion**:
- The correct answer is **Option D: Maltose, Lactose, Fructose**.
