$A$ tumor-inducing plasmid widely used in the production of transgenic plants is that of

"Crown gall" is caused by

Consider the following statements about $Bt$:
$I.$ The bacteria $Bacillus$ $thuringiensis$ $(Bt)$ are used to control butterfly caterpillars.
$II.$ Fresh spores of $Bt$ are mixed with water and sprayed on crops such as brassicas and fruit trees.
$III.$ Insect larvae,after eating these,are killed by the toxin released in their gut.
$IV.$ $Bt$ toxin genes have been introduced into plants to provide resistance to pests.
Which of the statements given above are correct?

Vitamin $A$ deficiency-induced blindness in developing countries can be reduced by using:

The main objective of the production/use of herbicide-resistant $GM$ crops is to

Transgenic plants are the ones