Write the structures of A,B C and D in the following reactions :
`C_(6)H_(5)COCloverset(H_(2)//Pd-BaSO_(4))rarr[A]overset("NaOH(conc.)")rarrB+Coverset(CH_(3)MgBr//H_(3)O^(+))rarr[D]`

Explanation

To solve the problem, we will identify the structures of compounds A, B, C, and D step by step based on the given reactions.

### Step 1: Identify Compound A
The starting compound is benzoyl chloride (C₆H₅COCl). When benzoyl chloride reacts with hydrogen in the presence of palladium on barium sulfate (Pd/BaSO₄), it undergoes a Rosenmund reduction. This reaction converts the acid chloride to an aldehyde by replacing the chlorine atom with a hydrogen atom.

**Structure of Compound A:**
- Benzaldehyde (C₆H₅CHO)

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