In this form of transport, a molecule or ion that can fit in a transport channel is free to
move through the channel in either direction and diffuse toward the side of the cell
where it is least concentrated. this form of transport is called facilitated diffusion.
why?

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

more words for this could be abiotic and biotic

abiotic: living organisms within an ecosystem

biotic: non-living organisms within an ecosystem

a=c and then d= c because of the band so you get ac/dc and you add them together you get sound waves

bradykinin is a physiologically and pharmacologically active peptide of the kinin group of proteins, consisting of nine amino acids.