The digestive systems shown are:
Figure A, Sponge - It uses intracellular digestion to process its food. Its body is having 'incurrent pore' through which water and food particles get in, from top water and wastes go out.
Figure B, Cnidarian - It processes its food by extracellular digestion. It has both mouth and anus through same opening from top. Water and food particles get in from top pass through Gastrovascular cavity, then water and wastes go out from top.
Figure C, Bird - It has one-way digestive tract with two openings. Water and food particles get in from mouth pass through Esophagus, Crop, Stomach, Gizzard, Intestine and finally water and waste comes out of anus.