A colourless solution of compound W is examined separately by adding a few drops of aqueous sodium hydroxide and a few drops of aqueous ammonia. In neither test is any precipitate formed. Which cation is present in W?
- A$\text{Al}^{3+}$
- B$\text{Ca}^{2+}$
- C$\text{Cu}^{2+}$
- D$\text{NH}_4^{+}$