Hirudin can be extracted from which transgenic plant?

$Bt$ cotton has which of the following special features?

Crystals of $Bt$ toxin produced by some bacteria do not kill the bacteria themselves because . . . . . .

What does $Bt$ stand for in the popular crop $Bt-cotton$?

Given below are $2$ statements: one is labelled as Assertion $(A)$ and other is labelled as Reason $(R)$.
Assertion $(A) :-$ Toxic insecticidal protein of Bacillus thuringiensis does not kill Bacillus itself.
Reason $(R) :-$ In Bacillus,$Bt$ toxin protein exists as inactive protoxins.
Correct answer from the options given below :

What is the source of complementary $dsRNA$?