The oxidising ability of the given anions follows the order

• Correct answer
  A

  $\mathrm{TiO}_{4}^{4-} < \mathrm{VO}_{4}^{3-} < \mathrm{CrO}_{4}^{2-} < \mathrm{MnO}_{4}^{-}$
• B

  $\mathrm{VO}_{4}^{3-} < \mathrm{CrO}_{4}^{2-} < \mathrm{MnO}_{4}^{-} < \mathrm{TiO}_{4}^{4-}$
• C

  $\mathrm{CrO}_{4}^{2-} < \mathrm{MnO}_{4}^{-} < \mathrm{VO}_{4}^{3-} < \mathrm{TiO}_{4}^{4-}$
• D

  $\mathrm{VO}_{4}^{3-} < \mathrm{TiO}_{4}^{4-} < \mathrm{CrO}_{4}^{2-} < \mathrm{MnO}_{4}^{-}$

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