$A$ transgenic food crop which may help in solving the problem of night blindness in developing countries is

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 triggers activation of protoxin to active $Bt$ toxin of Bacillus thuringiensis in bollworm?

Which disease-resistant cotton variety is developed using genetic engineering methods?

Explain with the help of one example how genetically modified plants can:
$(a)$ Reduce usage of chemical pesticides.
$(b)$ Enhance nutritional value of food crops.

$Bt-$ cotton is resistant to: