A 3 kg-box is sliding across a flat floor at an initial speed of 2.0 m/s and comes to a stop in 3 meters. If the only force acting on the box is force of kinetic friction. Draw a force diagram of the box. What is the net force acting on the box? What is the coefficient of friction between the box and floor?

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.

It really doesn't matter for any of the questions that you've listed.