Which of the following best demonstrates the principle of complementarity of structure and function? a. Bones can support and protect body organs because they contain hard mineral deposits. b. The heart and blood vessels circulate blood continuously to carry oxygen and nutrients to all body cells. c. The liver, brain, blood vessels, and stomach are each responsible for a necessary activity that no other organ can perform. d. Atoms, the tiny building blocks of matter, combine to form molecules such as water and proteins.