Statement $X$: Methanogens are responsible for the production of methane.
Statement $Y$: They can survive in acidic and high-temperature conditions.

• A
  Both Statement $X$ and Statement $Y$ are correct.
• B
  Both Statement $X$ and Statement $Y$ are incorrect.
• C
  Statement $X$ is correct,and Statement $Y$ is incorrect.
• D
  Both Statement $X$ and Statement $Y$ are correct,but Statement $Y$ is not the explanation of Statement $X$.