The respiratory organ of tadpole is

A. Skin

B. Lung

C. Gill

D. Air bladder

Frogs undergo metamorphosis during their life cycle. They begin as eggs, hatch into tadpoles, and gradually transform into adult frogs through several stages.

When a tadpole hatches, it resembles a small fish with a tail and breathes using gills. These gills have small flaps that absorb oxygen from the water as it passes through.

For the first few weeks, the tadpole feeds on plants and algae in the water. During this time, it also begins developing lungs, preparing it to breathe air once it becomes a frog.

As development continues, the tadpole first grows hind legs, then front legs, while its tail slowly becomes shorter. The tadpole uses the nutrients stored in its tail for energy during this stage.

Eventually, the tail disappears completely, and the tadpole transforms into a froglet. At this point, it leaves the water, becomes fully carnivorous, and breathes through both its lungs and its moist skin.

Thus, the correct answer is: gill.