Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because −
(a) bacteria are resistant to the toxin
(b) toxin is immature:
(c) toxin is inactive:
(d) bacteria encloses toxin in a special sac.
toxin is inactive:
In bacteria, the toxin is present in an inactive form, called prototoxin, which gets converted into active form when it enters the body of an insect.