Which three organ systems work together to take in oxygen and other nutrients and deliver them to an animal's body cells?
A. Respiratory, because it takes in gases from the external
environment
B. Circulatory, because blood absorbs nutrients and carries them to
other cells
c. Nervous, because it controls the body functions and responses to
stimuli
D. Digestive, because it breaks down the nutrients in food into
substances that can be used by cells