Assertion : Two sugar units joined by 1,2-glycosidic bond in sucrose.
Reason : It contains `C_(1)`-glucose and `C_(2)`-fructose glycosidic bond

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To solve the question, we will analyze the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Two sugar units are joined by a 1,2-glycosidic bond in sucrose."
- Sucrose is a disaccharide composed of two monosaccharides: glucose and fructose.

2. **Identifying the Components**:
- Sucrose is formed from α-D-glucose and β-D-fructose.
- In α-D-glucose, the anomeric carbon (C1) is the carbon that is involved in the glycosidic bond formation.
- In β-D-fructose, the carbon that participates in the bond is C2.

3. **Formation of the Glycosidic Bond**:
- When α-D-glucose and β-D-fructose undergo condensation, a water molecule is removed from the hydroxyl group (OH) on C1 of glucose and the hydroxyl group (OH) on C2 of fructose.
- This results in the formation of a glycosidic bond between C1 of glucose and C2 of fructose, which is specifically a 1,2-glycosidic bond.

4. **Understanding the Reason**:
- The reason states that "It contains C1-glucose and C2-fructose glycosidic bond."
- This is accurate as the glycosidic bond formed in sucrose indeed involves C1 of glucose and C2 of fructose.

5. **Conclusion**:
- Both the assertion and the reason are correct, and the reason accurately explains the assertion.
- Therefore, the correct answer to the question is that both the assertion and the reason are true and the reason is a correct explanation of the assertion.

### Final Answer:
Both the assertion and the reason are correct.

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