When ammonium cyanate is heated in the absence of air, urea, $\text{CO(NH}_2)_2$, is the only substance produced by the reaction. The reaction does not give any other products. What is the formula of the cyanate ion found in ammonium cyanate?
- A$\text{CON}_2^-$
- B$\text{CON}_2^{2-}$
- C$\text{OCN}^-$
- D$\text{OCN}^{2-}$