Answer:
1. break down of food into energy => oxygen
2. absorb x-rays in bones => calcium
3. cell membrane function => sodium
4. all organic compounds => carbon
Explanation:
Oxygen in an element which is required during cellular respiration which in turn generates energy in the form of ATP. Aerobic respiration is not possible in the absence of oxygen.
Calcium is an element which is abundantly present in bones and has great tendency to absorb x rays. It is because of calcium that our bones appear white when they are exposed to x rays.
Sodium ion is present in cells and play a very important role in maintaining cell membrane potential with the help of sodium potassium pump.
Carbon is an important element because it is an important constituent of all organic compounds. All organic compounds are chemically hydrocarbons i.e. compounds having short or long chains of carbon and hydrogen.