The hydrogen and oxygen atoms are held together by what bond

Which kind of worm has a closed circulatory system? a planarian b fluke c pinworm d an earthworm

What type of appendages do sponges cnidarians roundworms annelids mollusks arthropods echinoderms and vertebrate have? jointed, not jointed, absent  

Homo heidelbergensis was a tall, muscular hunter, who used both tools and weapons. because h. heidelbergensis was not a gatherer/forager, but ate a varied diet including meat and fish, we would expect to see what anatomical changes?