Which one of the following ions will give a coloured solution?

• A

  $\mathrm{C}{\mathrm{u}}^{+}$
• Correct answer
  B

  $\mathrm{F}{\mathrm{e}}^{2+}$
• C

  $\mathrm{Z}{\mathrm{n}}^{2+}$
• D

  $\mathrm{A}{\mathrm{g}}^{+}$

Hence, the correct answer is option: 'B'.