Answer
The correct order of answers is:f,h,d,b,c,a,g,e
Work Step by Step
Mollusks - f - mantle over body mass
Echinoderms - h - tube feet,spiny skin
Sponges - d - no tissues,filters out food
Cnidarians - b - nematocyst producers
Flatworms - c - simplest organ systems
Roundworms - a - complete gut,pseudocoelom
Annelids - g - segmented worms
Arthropods - e - jointed exoskeleton
