A metal $\text{(P)}$ on heating in nitrogen gas gives compound $\text{Q}\text{.}$ $\text{Q}$ on treatment with ${\mathrm{H}}_2\mathrm{O}$ gives a colourless gas which when passed through $\text{CuS}{\text{O}}_4$ solution gives a dark blue-violet coloured solution. $\text{P}$ and $\text{Q}$ respectively, are

• A

  Na and $\text{N}{\text{a}}_3\mathrm{N}$
• B

  Na and $\text{NaN}{\text{O}}_3$
• Correct answer
  C

  Mg and $\text{M}{\text{g}}_3{\mathrm{N}}_2$
• D

  Mg and $\text{Mg}(\text{N}{\text{O}}_3{)}_2$

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