A pond is full of tadpoles. Which respiratory surface are they using to take in oxygen?

1. A tadpole is the aquatic larva of an amphibian such as a frog or toad. 2. Living underwater, it must extract oxygen dissolved in the water, which gills are built to do. 3. It keeps using gills until the later stages of its development, when lungs take over. 4. Lungs serve the adult frog and all mammals, and the adult frog also exchanges gas through its skin. 5. Spiracles are the openings into an insect's tracheal tubes, and book lungs belong to spiders — neither is found in a tadpole. _Source: NECTA CSEE 2021 Biology 033, Question 1: Multiple Choice, item (i)_