Statement $-I:$ The interaction where one species is benefitted and the other is neither benefitted nor harmed is called commensalism.
Statement $-II:$ Barnacles growing on the back of a whale is an example of commensalism.

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