Match correctly from column-I and column-II

Column-I	Column-II
(A) H₂ / Pd-BaSO₄	(i) Etard oxidation
(B) CrO₂Cl₂ + CS₂	(ii) Stephen’s reduction
(C) SnCl₂ + HCl	(iii) Gattermann-Koch reaction
(D) CO + HCl + AlCl₃	(iv) Rosenmund reduction

The correct matching between Column-I and Column-II is A-iv, B-i, C-ii, D-iii.

Let us analyze each reagent in Column-I and map it to its corresponding named reaction in Column-II:

(A) H₂ / Pd-BaSO₄:
Hydrogenation using palladium catalyst poisoned with barium sulfate (H₂ / Pd-BaSO₄) is known as the Rosenmund reduction. It selectively reduces acyl chlorides (acid chlorides) to aldehydes.
Hence, (A) matches with (iv).

(B) CrO₂Cl₂ + CS₂:
Chromyl chloride (CrO₂Cl₂) in carbon disulfide (CS₂) followed by hydrolysis oxidizes methylbenzene (toluene) to benzaldehyde. This reaction is called the Etard oxidation.
Hence, (B) matches with (i).

(C) SnCl₂ + HCl:
Reduction of nitriles (alkyl cyanides) using stannous chloride (SnCl₂) and hydrochloric acid (HCl) followed by hydrolysis yields aldehydes. This reaction is known as the Stephen's reduction.
Hence, (C) matches with (ii).

(D) CO + HCl + AlCl₃:
Formylation of benzene or its derivatives using carbon monoxide (CO) and hydrogen chloride (HCl) in the presence of anhydrous aluminum chloride (AlCl₃) yields benzaldehyde. This is known as the Gattermann-Koch reaction.
Hence, (D) matches with (iii).

Combining all the correct pairs:
(A) → (iv)
(B) → (i)
(C) → (ii)
(D) → (iii)