Given below are two statements:
Statement $I$: Diazotrophs are the nitrogen-fixing microorganisms,which are exclusively symbiotic.
Statement $II$: Organic fertilizers include farmyard manure,compost,and green manure.
In light of the above statements,choose the most appropriate answer from the options 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 and statement $II$ is incorrect.
• D
  Statement $I$ is incorrect and statement $II$ is correct.