Match List-I with List-II:List-IList-IIA. Symbiotic nitrogen-fixing b…

The correct answer is Option (3) → A-II, B-I, C-IV, D-III

Two rows of List-I are nitrogen-fixing bacteria (biofertilisers) and two are biocontrol agents. Each has to be paired with the right organism or target.

(A) Symbiotic nitrogen-fixing bacterium — this matches (II) Rhizobium. Rhizobium forms nodules on the roots of leguminous plants and fixes nitrogen while living in symbiosis with them.

(B) Dragonflies — this matches (I) Mosquitoes. Dragonflies are predators used to get rid of mosquitoes, while ladybirds are used against aphids.

(C) Bacillus thuringiensis — this matches (IV) Butterfly caterpillars. Its spores are sprayed on plants; when larvae eat them, the toxin released in the gut kills the caterpillars.

(D) Free-living N₂-fixing bacterium — this matches (III) Azotobacter. Azotobacter and Azospirillum fix nitrogen while living free in the soil, without forming nodules.

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

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).”
Microbes as Biofertilisers – “… You have studied about the nodules on the roots of leguminous plants formed by the symbiotic association of Rhizobium. These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as nutrient. Other bacteria can fix atmospheric nitrogen while free-living in the soil (examples Azospirillum and Azotobacter), thus enriching the nitrogen content of the soil.”