Match List-I (biocontrol agent) with List-II (what it controls):List-…

The correct answer is Option (2) → A-III, B-I, C-IV, D-II

Biocontrol uses living organisms in place of chemicals to control pests and plant diseases. Two of the agents here are predatory insects and two are microbes, and each has its own target.

(A) Ladybird — this matches (III) Aphids. The familiar red-and-black beetle feeds on aphids and keeps them in check.

(B) Dragonflies — this matches (I) Mosquitoes. Dragonflies are useful for getting rid of mosquitoes.

(C) Bacillus thuringiensis — this matches (IV) Butterfly caterpillars. Larvae that eat the sprayed Bt spores are killed by the toxin released in their gut.

(D) Trichoderma — this matches (II) Several plant pathogens. This free-living fungus of root ecosystems is being developed for the treatment of plant diseases.

So the matching is A-III, B-I, C-IV, D-II.

NCERT Extract:
Microbes as Biocontrol Agents – “The very familiar beetle with red and black markings – the Ladybird, and Dragonflies are useful to get rid of aphids and mosquitoes, respectively. An example of microbial biocontrol agents that can be introduced in order to control butterfly caterpillars is the bacteria Bacillus thuringiensis (often written as Bt). … A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma. Trichoderma species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens.”