3. in every chemical or physical change
The element iodine (I) is important for the fast and hastened metamorphosis of frog-tadpoles. As amphibians, the tadpoles can live in water and land but when they are born they are iodine-deficient. Tadpoles that do not receive ample amount of iodine become tadpoles until the end of their days.
Zirconium cannot be broken down by a chemical change, because it is an element. The others are all molecules.
If I'm correct the answer should be a series circuit :) Hopefully this helps you out
