Reaction of alkyl halides with cyanide - nitrile vs isonitrile formation

2023 Manipur 1 question

1. Which amongst the following reactions of alkyl halides produces isonitrile as a major product? (A) R–X + HCN $\rightarrow$ (B) R–X + AgCN $\rightarrow$ (C) R–X + KCN $\rightarrow$ (D) R–X + NaCN $\xrightarrow{H_2O/C_2H_5OH}$