Which of the following is used for the safety testing of the polio vaccine?

Choose the appropriate option for chemical safety testing.

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?

The maximum number of existing transgenic animals is of:

Some genes of transgenic animals are made .....$X$..... to certain .....$Y$..... substances.

Which of the following is known as toxicity/safety testing in the context of transgenic animals?