Crystals of $Bt$ toxin produced by some bacteria do not kill the bacteria themselves because

Which of the following is commonly used for the transfer of foreign $DNA$ into crop plants?

Hairy root disease of dicot plants is caused by-

What does $Bacillus$ $thuringiensis$ produce that is responsible for the death of certain insects?

Golden rice
$I$. It is a transgenic variety of rice.
$II$. It contains a good quality of $\beta$-carotene (provitamin-$A$).
$III$. $\beta$-carotene is a principal source of vitamin-$A$.
$IV$. The grains of the rice are yellow in colour due to $\beta$-carotene. The rice is commonly called golden rice.
Which of the statements given above are correct?

Some of the characteristics of $Bt$ cotton are