Which of the regents will convert a nitrile to corresponding aldehyde?

The correct answer is option 1. \(\text{i. DIBAL-H,  ii. }H_3O^+\)

To convert a nitrile to the corresponding aldehyde, you need a reagent that can selectively reduce the nitrile group (\(-\text{CN}\)) to an aldehyde group (\(-\text{CHO}\)) without further reducing it to an alcohol. The appropriate reagent for this transformation is:

\(\text{i. DIBAL-H,  ii. }H_3O^+\)

DIBAL-H (Diisobutylaluminum Hydride) is a selective reducing agent that can reduce nitriles to aldehydes when used under controlled conditions. DIBAL-H is known for its ability to stop the reduction at the aldehyde stage, avoiding further reduction to alcohols.

\(H_3O^+\) (Acidic work-up) is used to hydrolyze the intermediate product formed by the reaction of DIBAL-H with the nitrile, resulting in the aldehyde.