Assertion : Aromatic aldehydes and formaldehyde undergo Cannizzaro reaction.
Reason : Those aldehydes which have `alpha`-H atom undergo Cannizzaro reaction.

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.

Explanation

To solve the question, we need to analyze the assertion and the reason provided:

**Assertion:** Aromatic aldehydes and formaldehyde undergo Cannizzaro reaction.
**Reason:** Those aldehydes which have alpha-H atom undergo Cannizzaro reaction.

### Step-by-Step Solution:

1. **Understanding Cannizzaro Reaction:**
- The Cannizzaro reaction is a redox reaction that occurs with aldehydes that do not have an alpha-hydrogen atom. In this reaction, one molecule of the aldehyde is oxidized to a carboxylic acid, while another molecule is reduced to an alcohol.

2. **Identifying Aromatic Aldehydes and Formaldehyde:**
- Aromatic aldehydes include compounds like benzaldehyde (C6H5CHO), which lacks an alpha-hydrogen atom because the carbon adjacent to the carbonyl group (the carbonyl carbon) is part of the aromatic ring.
- Formaldehyde (HCHO) also does not have an alpha-hydrogen atom as it has no carbon atoms adjacent to the carbonyl carbon.

3. **Analyzing the Assertion:**
- Since both aromatic aldehydes (like benzaldehyde) and formaldehyde lack alpha-hydrogens, they can undergo the Cannizzaro reaction. Therefore, the assertion is **correct**.

4. **Analyzing the Reason:**
- The reason states that aldehydes with alpha-hydrogen atoms undergo the Cannizzaro reaction. This is **incorrect**. Aldehydes that have alpha-hydrogens typically undergo aldol condensation reactions instead of Cannizzaro reactions.

5. **Conclusion:**
- The assertion is true, while the reason is false. Therefore, the correct answer is that the assertion is correct, but the reason is incorrect.

### Final Answer:
- Assertion is true, Reason is false.