Calculate the average speed of spacecraft orbiting mars

That completely depends on the size of the orbit. Similarly at Earth, a TV satellite takes 1 day for an orbit, but the Moon takes 27.3 days.

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.