Evolutionary adaptations that help some animals directly exchange matter between the cells of their body and the environment include _________.
A. a gastrovascular cavity, a two-layered body, and a torpedo-like body shape
B. an external respiratory surface, a small body size, and a two-cell-layered body
C. a large body volume, a long, tubular body, and a set of wings
D. an unbranched internal surface, a small body size, and thick covering