Assertion : By hydrogenation, vegetable oils are converted into vanaspati ghee.
Reason : Vegetable oils contain at least one double bond inb their constituents.

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 given question, we need to analyze the assertion and reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "By hydrogenation, vegetable oils are converted into vanaspati ghee."
- Hydrogenation is a chemical reaction where hydrogen is added to unsaturated compounds (which contain double bonds) to convert them into saturated compounds.

2. **Understanding the Reason**:
- The reason states that "Vegetable oils contain at least one double bond in their constituents."
- Vegetable oils are primarily unsaturated fats, meaning they have one or more double bonds in their fatty acid chains.

3. **Linking Assertion and Reason**:
- Since vegetable oils contain double bonds, they can undergo hydrogenation. During this process, hydrogen is added to these double bonds in the presence of a catalyst (commonly nickel), converting the unsaturated fats into saturated fats, which is what vanaspati ghee essentially is.

4. **Conclusion**:
- Both the assertion and the reason are true.
- The reason correctly explains why the assertion is true, as the presence of double bonds in vegetable oils is essential for the hydrogenation process to occur.

### Final Answer:
Both the assertion and reason are true, and the reason is the correct explanation of the assertion.