Statement $X$: Collection of plant and animal species is the primary source of taxonomic studies.
Statement $Y$: Taxonomic studies help in preparing flora and fauna of different regions.
Statement $Z$: Based on taxonomic studies,the geographical distribution of organisms can be understood.

• A
  $X$ and $Y$ are correct,and $Z$ is incorrect.
• B
  $X$ and $Z$ are correct,and $Y$ is incorrect.
• C
  $X, Y$,and $Z$ are all correct.
• D
  $X$ is correct,and $Y$ and $Z$ are incorrect.