In general, less complex animals are:
                                                                           
                                                       
                                                                   
A. more likely to rely on specialized mouth parts for digestion.
B. more likely to perform extracellular digestion than intracellular digestion.
C. more likely to have a gastrovascular cavity than to have a digestive tract.
D. more likely to have two body openings than to have one body opening.