What does $Bt$ stand for?

Main objective of production/use of herbicide resistant $GM$ crops is to
$(A)$ -Reduce herbicide accumulation in food articles for health safety.
$(B)$ -Eliminate weeds in the field without the use of herbicides.
$(C)$ -Eliminate weeds from the field without the use of manual labour.
$(D)$ -Soil pollution and biomagnification caused by herbicides.
Which of the following statements are correct?

$RNA$ interference $(RNAi)$ is used to produce transgenic plants resistant to which of the following?

The toxin proteins isolated from $Bacillus$ $thuringiensis$, coded by which of the following genes would control cotton bollworms and corn borer, respectively?

With which cells of the insect gut does the $Cry$ protein bind to create pores?

$RNA$ interference involves