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Identify the combination in which a carboxylic acid group is transformed into an aldehyde group.

1. (a) (I) (iv) (P)
2. (b) (I) (iii) (S)
3. (c) (II) (iii) (P)
4. (d) (II) (iii) (Q)

Correct answer: (a) (I) (iv) (P)

Solution

A carboxylic acid can be converted to an aldehyde only through a selective reduction sequence. Among the given combinations, option (a) matches the required transformation.

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