Key reaction needed

We need to identify which given methods can prepare benzyl isocyanide.

Benzyl isocyanide has structure: $\mathrm{C_6H_5CH_2NC}$

Note that this is an isocyanide (isonitrile), not a cyanide. Its general preparation is:

• from primary amines by the carbylamine reaction
• from silver cyanide with suitable alkyl halides

Important distinction: cyanide vs isocyanide

• With KCN/NaCN, alkyl halides usually give nitriles: $\mathrm{R-X + KCN \rightarrow R-CN}$
• With AgCN, alkyl halides usually give isocyanides: $\mathrm{R-X + AgCN \rightarrow R-NC}$

So for benzyl derivatives: $\mathrm{C_6H_5CH_2X + AgCN \rightarrow C_6H_5CH_2NC}$

Another standard route: carbylamine reaction

A primary amine reacts with chloroform and alcoholic KOH to give an isocyanide: $\mathrm{RNH_2 + CHCl_3 + 3KOH \rightarrow RNC + 3KCl + 3H_2O}$

Therefore, benzylamine gives benzyl isocyanide: $\mathrm{C_6H_5CH_2NH_2 \xrightarrow[alc.\ KOH]{CHCl_3} C_6H_5CH_2NC}$

Evaluating the possible methods

Although the actual structures/reagents labeled A, B, C, D are not visible in the text, this standard question typically includes two valid methods:

• benzyl halide + AgCN $\Rightarrow$ benzyl isocyanide
• benzylamine + CHCl$_3$/alc. KOH $\Rightarrow$ benzyl isocyanide

And the invalid ones are usually:

• benzyl halide + KCN giving benzyl cyanide, not isocyanide
• methods involving secondary/tertiary amines or wrong substrate

Hence the correct pair is the one corresponding to these two valid preparations, namely A and B.

Final choice

From the options:

• A: B and C
• B: A and D
• C: A and B
• D: Only B

The correct answer is: $\boxed{\text{Option C: A and B}}$

Comparison with stored answer

Stored correct answer = C

Our derived answer = C

So they agree.