The release of which one of the following into ponds and wells helps in controlling the mosquitoes?

Answer: (c) Gambusia fish

Gambusia (mosquitofish) eats mosquito larvae at the water surface; it is released into ponds and wells to control malaria.

The idea

Mosquitoes lay eggs on still water, and the larvae hang just under the surface. A small fish that feeds at the surface eats them before they can become adults. Using a living thing to control a pest is called biological control.

Mosquito lays eggs on water → Larvae hang at the surface → Gambusia eats them → Fewer adult mosquitoes → Less malaria and dengue

Why the others are wrong

(b) The dogfish is a small shark — a sea animal.

(d) Snails graze algae.

Also know

Gambusia comes from North America and has a cost: it also eats the eggs and young of local fish and frogs and is now counted as an invasive species. The guppy is used in the same way.