A steel rod is initially at \( 20^\circ\mathrm{C} \) and has a length of \( 2\,\mathrm{m} \). It has a cross-sectional area of \( 0.001\,\mathrm{m^2} \) If it is heated to \( 120^\circ\mathrm{C} \), how large a force must be applied to its end to restore the original length? Use \( 12\times10^{-6}\mathrm{(C^\circ)^{- 1}} \).​

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.

C. it comes from the core of the earth.