Consider the following reagents:
I. $\mathrm{R}-\mathrm{NC}$
II.${\mathrm{CHCl}}_3$
III.${\mathrm{COCl}}_2$
IV.${\mathrm{NaNO}}_2+\mathrm{HCl}$
Which of the following species are involved in the carbylamine test for primary amines?

Aliphatic and aromatic primary amines on heating with chloroform and ethanolic KOH form isocyanides or carbylamines which is known as carbylamine test and is used to test only primary amine.
${\mathrm{RNH}}_2+{\mathrm{CHCl}}_2+3\mathrm{KOH}\stackrel{\mathrm{Heat}}{\to }\mathrm{RNC}+3\mathrm{KCl}+3{\mathrm{H}}_2\mathrm{O}$