Given below are two statements :
Statement $I$: In group $13$, the stability of $+1$ oxidation state increases down the group.
Statement $II$: The atomic size of gallium is greater than that of aluminium.
In the light of the above statements, choose the most appropriate answer from the options given below:

• A
  Statement $I$ is incorrect but Statement $II$ is correct
• B
  Both Statement $I$ and Statement $II$ are correct
• C
  Both Statement $I$ and Statement $II$ are incorrect
• D
  Statement $I$ is correct but Statement $II$ is incorrect