These compounds can be used as nitrogenous fertilisers. Which compound has the smallest percentage by mass of nitrogen?
- A$(\text{NH}_2)_2\text{CO} \; [M_r = 60]$
- B$(\text{NH}_4)_2\text{SO}_4 \; [M_r = 132]$
- C$(\text{NH}_4)_3\text{PO}_4 \; [M_r = 149]$
- D$\text{NH}_4\text{NO}_3 \; [M_r = 80]$