Which of the following controls/control the growth of bollworms?

The correct answer is Option (1) → CryIAc and CryIIAb genes

Option (1) CryIAc and CryIIAb genes — Correct. The proteins of these cry genes of Bacillus thuringiensis are toxic to the cotton bollworms. Bt cotton carries these genes.

Option (2) CryIAb gene — Incorrect. It is also a Bt toxin gene, but its protein controls the corn borer, a pest of maize. Each Bt toxin is specific to its insect group.

Option (3) RNAi — Incorrect. RNA interference silences a chosen mRNA. It was used to protect tobacco roots from the nematode Meloidogyne incognita, not cotton from bollworms.

Option (4) dsRNA — Incorrect. Double-stranded RNA is the molecule that does the silencing in RNAi. It binds the matching mRNA of the nematode and stops its translation.

NCERT Extract:
Biotechnological Applications in Agriculture – “… Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton (Figure 10.1). The choice of genes depends upon the crop and the targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene named cry. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, that of cryIAb controls corn borer.”