When ammonium cyanate is heated with air excluded, the reaction gives only urea, $\text{CO(NH}_2)_2$. No other products are produced in this reaction. What is the formula of the cyanate ion in ammonium cyanate?
- A$\text{CON}_2^-$
- B$\text{CON}_2^{2-}$
- C$\text{OCN}^-$
- D$\text{OCN}^{2-}$