Study the following statements.
$I$. Pollen grains of many species cause severe allergies and bronchial afflictions in some people,often leading to chronic respiratory disorders.
$II$. Pollen grains are rich in nutrients.
$III$. Carrot grass came into India as a contaminant with imported wheat.

• A
  Statements $I$ and $III$ are correct,but statement $II$ is incorrect.
• B
  All statements are incorrect.
• C
  Statements $I$ and $II$ are correct,but statement $III$ is incorrect.
• D
  All given statements are correct.