9. What system breaks food down into energy for the body? A. Circulatory system C. Muscular system B. Digestive system D. Respiratory system 10. What system controls voluntary and involuntary life functions? A. Circulatory system C. Nervous system B. Digestive system D. Muscular system 11. What two organs make up the central nervous system? A. brain and spinal cord B. neurons and receptors C. cerebrum and cerebellum D. somatic nerves and autonomic nerves 12. The wall of the alveoli is what kind of tissue? A. muscle tissue C. epithelial tissue B. nervous tissue D. connective tissue 13. What is the relationship between tissues and organs? A. organ develop into tissues B. organs are made up of tissues C. organs are endorsed by tissues D. tissues contain one or more organ 14. Which pair of organs includes only the endocrine glands? A. Adrenal and ovary C. Pancreas and parathyroid B. Parathyroid and adrenal D. Thymus and testes 15. Which of the following are proteins that fight off diseases? A. antibodies C. antigens B. B- cells D. memory cells​