Iron rusts when exposed to air → chemical property
I believe the answer is gills
Fish's use gills to breathe, so tadpoles should use gills too
hope this helps
(got the info from a documentary i watched a couple years ago)
It is a compound because a compound is two or more different elements chemically combined.
I would say soil would be your best option. This is because out of all these, soil collects a lot of different substances and could have easily absorbed something that then killed the organism.
