The pair of ions with paramagnetic nature and same number of electrons is

• A

  $\mathrm{Lu}^{3+}, \mathrm{Yb}^{2+}$
• B

  $\mathrm{Eu}^{3+}, \mathrm{Pm}^{2+}$
• Correct answer
  C

  $\mathrm{Eu}^{2+}, \mathrm{Gd}^{3+}$
• D

  $\mathrm{La}^{3+}, \mathrm{Ce}^{4+}$

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