The correct option is C cotton bollworms
The crystalline (Cry) protein synthesized by Bacillus thuringiensis exists as an inactive protoxin, but once a target insect ingests the Cry protein, then it gets solubilized in their alkaline midgut. It gets activated by a protease present which leads to the binding of it to the specific receptors located in the insect midgut epithelial cells creating pores that eventually lead to the death of the insect.
Most Bt-toxins are effective against specific insect groups, for example CryⅠAc and CryⅡAb control the cotton bollworms whereas CryⅠAb controls corn borer.