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 :

• A
  Both $(A)$ and $(R)$ are correct and $(R)$ is the correct explanation of $(A)$
• B
  Both $(A)$ and $(R)$ are correct but $(R)$ is not the correct explanation of $(A)$
• C
  $(A)$ is correct but $(R)$ is not correct
• D
  $(A)$ is not correct but $(R)$ is correct