……….. gene control the corn borer.

All the following statements are correct for Bt toxin but one is wrong. Which one is wrong?

$BT$  cotton is resistant to

$B t$ cotton variety that was developed by the introduction of toxin gene of Bacillus thuringiensis $(Bt)$ is resistant to 

Explain with the help of one example how genetically modified plants can :

$(a) $ Reduce usage of chemical pesticides.

$(b)$ Enhance nutritional value of food crops