Which of the following on reactions with nitrous acid, followed by treatment with NaOH produces a blue coluration?

• A

  $\mathrm{R}\mathrm{C}{\mathrm{H}}_2\mathrm{N}{\mathrm{O}}_2$
• B

  ${\mathrm{R}}_3\mathrm{C}\mathrm{N}{\mathrm{O}}_2$
• Correct answer
  C

  ${\mathrm{R}}_2\mathrm{C}\mathrm{H}\mathrm{N}{\mathrm{O}}_2$
• D

  $\mathrm{P}\mathrm{h}\mathrm{N}{\mathrm{O}}_2$

Hence, the correct answer is option: 'C'.