How is inactive Bt-toxin converted into active form?

Consider the following statements. A. Bt toxin is produced by a bacterium called Bacillus thuringiensis. B. The Bt toxin is coded by a gene named cry. C. Bt inactive toxin is converted into an active form of toxin due to the acidic pH of the insect gut. D. The Bt proteins encoded by the genes cryIAc and cryIIAb control the corn borer. Of the above statements:

Bt endotoxin that exists as inactive protoxin is converted in to active toxin once bollworm ingests it due to

Bt toxin is

Bt toxin is

Assertion (A) : Acidic pH of insect converts inactive Bt toxin into active form Reason (R) : Most of Bt toxins are insect group specific.

In Bt cotton, the Bt toxin present in plant tissue as pro-toxin is converted into active toxin due to