A bicyclist rides from their home (consider their home as the origin) 20 miles north and then 50 miles to the south. What is the bicyclist’s final displacement?
A) 30 miles north
B) 30 miles south
C) 70 miles north
D) 70 miles south

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.