Given below are two statements.
Statement $I$ - During respiration the respiratory substrate directly unite with oxygen.
Statement $II$ - The primary process of respiration consists of removal of hydrogen from the respiratory substrate.
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.