A : In crossed Cannizzaro's reaction in between HCHO and `C_(6)H_(5)CHO`, HCHO is oxidised.
R : `OH^(-)` firstly attacks on HCHO. So, HCHO is oxidised.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4).

Answer

To solve the question regarding the crossed Cannizzaro reaction between formaldehyde (HCHO) and benzaldehyde (C₆H₅CHO), we will analyze the statements provided:

**Statement A:** In the crossed Cannizzaro reaction between HCHO and C₆H₅CHO, HCHO is oxidized.

**Statement R:** OH⁻ firstly attacks HCHO. So, HCHO is oxidized.

### Step-by-Step Solution:

1. **Understanding Cannizzaro Reaction:**
- The Cannizzaro reaction occurs when aldehydes that do not have alpha-hydrogens undergo disproportionation in the presence of a strong base (like NaOH or KOH).
- In this reaction, one molecule of the aldehyde is oxidized to a carboxylic acid, while another molecule is reduced to an alcohol.

2. **Identifying the Reactants:**
- The two aldehydes involved in the reaction are formaldehyde (HCHO) and benzaldehyde (C₆H₅CHO).
- HCHO has no alpha-hydrogens, making it suitable for the Cannizzaro reaction. Benzaldehyde also lacks alpha-hydrogens.

3. **Mechanism of the Reaction:**
- In the presence of OH⁻ (hydroxide ion), it acts as a nucleophile and attacks the carbonyl carbon of HCHO.
- The attack results in the formation of a tetrahedral intermediate, which then leads to the formation of a carboxylate ion (HCOO⁻) and a hydride ion (H⁻).

4. **Hydride Transfer:**
- The hydride ion (H⁻) generated from the oxidation of HCHO can then be transferred to the electrophilic carbon of benzaldehyde (C₆H₅CHO).
- This transfer results in the reduction of benzaldehyde to benzyl alcohol (C₆H₅CH₂OH).

5. **Final Products:**
- The final products of the reaction are formic acid (HCOOH) from the oxidation of HCHO and benzyl alcohol (C₆H₅CH₂OH) from the reduction of benzaldehyde.

6. **Conclusion:**
- Since HCHO is indeed oxidized to formic acid, Statement A is correct.
- The reason provided (Statement R) is also correct, as OH⁻ does attack HCHO first, leading to its oxidation.
- Therefore, both statements A and R are true, and R is the correct explanation for A.

### Final Answer:
Both Statement A and Statement R are correct, and R is the correct explanation for A.

---