What is the formula of calcium nitride?

A.     ${\text{C}}{{\text{a}}_{\text{3}}}{{\text{N}}_{\text{2}}}$

B.     ${\text{C}}{{\text{a}}_{\text{2}}}{{\text{N}}_{\text{3}}}$

C.     ${\text{Ca(N}}{{\text{O}}_{\text{2}}}{{\text{)}}_{\text{2}}}$

D.     ${\text{Ca(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}$

A