When a few drops of ammonia solution is added to copper(II) ions, a blue precipitate of copper(II) hydroxide is formed. CuSO₄(aq) + 2NH₃(aq) + 2H₂O(ℓ) ⇌ Cu(OH)₂(s) + (NH₄)₂SO₄(aq) However, when ammonia solution is added in excess, the blue precipitate re-dissolves to form a deep blue solution of tetraamine copper(II) hydroxide. Cu(OH)₂(s) + 4NH₃(aq) → [Cu(NH₃)₄](OH)₂(aq). Therefore, the correct answer is option A.