Which one of the following statements related to lanthanons is incorrect?

• A

  Europium shows $+2$oxidation state.
• B

  The basicity decreases as the ionic radius decreases from $\mathrm{Pr}$ to $\mathrm{Lu}$.
• Correct answer
  C

  All the lanthanons are much more reactive than aluminium.
• D

  $\mathrm{Ce}\left(+4\right)$ solutions are widely used as oxidizing agent in volumetric analysis.

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