Enzymes are proteins that catalyse (speed up) vital chemical reactions inside the body. Enzymes will only function properly under a small range of certain conditions, such as preferred pH and temperature. If any conditions are outside their specific range then the enzymes cannot function. This could cause the organism to die. Homeostasis relies on automatic control systems that include nervous responses (nervous system) or chemical responses (endocrine system). Receptors and effectors are also needed
because cell theory states that living things are composed of one or more cells, that the cells is the basic unit of life, and that cells arise from existing cells.
My best guess would be c because b makes no since we as humans do not have photosynthesis and are considered living organisims, d is also wrong because the brain requires oxygen, and its not a because the brain is made of cells.
