Ammonia forms the complex `[Cu(NH_3)_4]^(2+)` with copper ions in alkaline solution but not in acid solution. The reasons for it is:

Options

A. In acidic solution , protons coordinate with ammonia molecules forming `NH_4^+` ions and `NH_3` molecules are not available
B. In alkaline solutions insoluble `Cu(OH)_2` is precipitated which is soluble in excess of any alkali
C. Copper hydroxide is an amphoteric substance
D. In acidic solutions hydration protects copper ions

Answer

A