Given below are two statements.
Statement $I$ - According to Darwin,the gradual,inheritable variations over a long period of time lead to speciation.
Statement $II$ - According to Hugo de Vries,mutations are the cause of variations.
In the light of above statements,select the correct option given below:

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