Statement $I$: $ELISA$ works on the principle of antigen-antibody interaction.
Statement $II$: Infection by a pathogen can be detected by the presence of antigens or by detecting the antibodies synthesized against the pathogen.

• A
  Statement $I$ is true but statement $II$ is wrong
• B
  Statement $I$ and $II$ both are true
• C
  Statement $I$ is wrong but statement $II$ is true
• D
  Statement $I$ and $II$ both are wrong