In general, more complex animals are

A. More likely to rely on chemical digestion than to rely on mechanical digestion
B. more likely to perform intracellular digestion than extracellular digestion
C. more likely to have one body opening than to have two body openings
D. more likely to have a digestion tract than to have a gastrovascular cavity

Question

In general, more complex animals are

A. More likely to rely on chemical digestion than to rely on mechanical digestion
B. more likely to perform intracellular digestion than extracellular digestion
C. more likely to have one body opening than to have two body openings
D. more likely to have a digestion tract than to have a gastrovascular cavity

anonymous · Answer

Complex Animals are most likely to be vertebrates (and some invertebrates) since they have more body functions, have more than one anatomical system (Nervous, skeletal, Reproductive, etc.)  Compared to "Simple Animals" (Like starfishes and Sponges).

Simple animals does chemical digestion, or intracellular digestion, and only have one body opening... this leaves you what choice for the complex animal?