The substance that would be added in order to reverse the reaction would be any substance that is found in the product side. Adding a substance that tends to be a product will shift the equilibrium of the system and will allow the reaction to produce the substances that is found in the reactant side.
Answer:
C.
It controls the entry and exit of substances.
That's hard. The action might be when you go to lift your feet off the ground and the reaction force is letting your feet touch the ground again while taking a stride. Hope this helps.
