Consider the following statements:
$I$. Transgenic animals are more sensitive to toxic substances than non-transgenic animals.
$II$. Useful biological products can be produced by introducing into transgenic animals the portion of $DNA$ which codes for a particular product.
$III$. Brazzein is a protein produced by a West African plant,$Pentadiplandra$ $brazzeana$,which is approximately $2000$ times as sweet as sugar.
Which of the statements given above are correct?

• A
  $I$,$II$ and $III$
• B
  $I$ and $II$
• C
  $I$ and $III$
• D
  None of these