Help quick!
which choice and why?

Which element provides strength to the exoskeleton of clams and oysters

Advances in technology have enabled scientists and researchers to better study the evolutionary relationships between species

Food webs - transferring energy and matter from one level to another. here you see four food webs. one or more are incorrect. which food web(s) show the correct sequence of organisms, from start to top level consumer? a) a b) d c) c d) a and d