Genetically Modified Crops

To solve the problem, let's evaluate each statement individually by providing explanations based on biological concepts:

Statement I: "Bt toxins are insect group specific and coded by a gene cry IAc." This statement is true. Bacillus thuringiensis (Bt) produces specific toxins known as Cry proteins which target certain groups of insects. The gene cry IAc is one of the many cry genes responsible for coding these toxins. These proteins are highly specific to the insect order, for example, lepidopteran pests.

Statement II: "Bt toxin exists as inactive protoxin in B. thuringiensis. However, after ingestion by the insect the inactive protoxin gets converted into active form due to acidic pH of the insect gut." This statement is false. While it is true that Bt toxin is produced as an inactive protoxin in Bacillus thuringiensis, the conversion to its active form does not occur due to the acidic pH of the insect's gut. Instead, the activation is facilitated by the alkaline conditions present in the midgut of susceptible insects, where specific gut proteases cleave the protoxin to activate it.

Given these explanations, the correct conclusion is that Statement I is true but Statement II is false.

Therefore, the applicable choice is: Statement I is true but Statement II is false