Correct option is B
Bt-toxin (Bacillus thuringiensis toxin) is a crystalline protoxin protein produced by the bacterium Bacillus thuringiensis. It is not active in its original form. When ingested by insect larvae (especially Lepidopteran pests),
Gets activated in the alkaline gut of insect larvae
Binds to specific receptors on midgut cells, causing cell rupture
Used in genetically modified crops (e.g., Bt cotton) for pest resistance