2 A boy of mass 50 kg runs up a hill of vertical height 300 m in 20 minutes. Calculate:
a) the average vertical force he uses to lift himself up the
hillside
b) the work he does climbing the hill
c) his average power.

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.

Iwould have to say sorry i can't elaborate more. hope this though!