Which statement best explains the internal structure of animal bodies? a.  animals are made up of cytoplasm. a group of cytoplasm forms a nucleus. multiple nuclei form an organ. multiple organs form energy. b. animals are made up of cells. cells work together to form organs. organs form complex systems that produce energy. energy results in animal life. c. animals are made up of tissues. layers of tissues form organ systems. organ systems create skeletal structure. the skeletal structure is covered by dermis. d. animals are made up of cells that share a function and group together to form tissues. tissues make up organs. organs that work together form an organ system.