The reaction with \( \text{AgCN} \) leads to the formation of alkyl isocyanide due to the covalent character of \( \text{AgCN} \).
The Correct Answer is: AgCN
\( \text{M} \xrightarrow{\text{CH}_3\text{MgBr}} \text{N} + \text{CH}_4 \uparrow \xrightarrow{\text{H}^+} \text{CH}_3\text{COCH}_2\text{COCH}_3 \)