Step 1: The assertion (A) says that the protoxin of Bacillus thuringensis becomes active in the gut of insects. This is true as the protoxin is inactive in its crystalline form and needs to be activated by specific conditions in the gut of the insect.
Step 2: The reason (R) states that the alkaline pH of the insect’s gut helps to solubilize the crystals of the toxin and activates it. This is also true as the alkaline pH of the gut is essential in converting the protoxin into the active form that kills the insect.
Step 3: Both assertion (A) and reason (R) are true, and reason (R) provides the correct explanation for why assertion (A) is true. Therefore, the correct answer is that both (A) and (R) are correct and (R) is the correct explanation of (A).