Answer:
The electron transport chain is the third and final step of cellular respiration. At the end of the electron transport chain, the hydrogen from the coenzymes meets the oxygen which the cell has consumed and reacts with it to form water. Therefore, water is created as a byproduct of the metabolism reaction.
It would be B.pyramid of numbers
Hope this helps
Have a great day/night
Its the letter B because its the circulatory system
SO2: inorganic compound
k: element
Cl2: inorganic elemental molecule
C6H6: organic compound