Answer to Question 1
The ocean acts as a reservoir for carbon dioxide because it is able to store large amounts of it. There is a high theoretical maximum for carbon dioxide which is not reached in the ocean. There is 60 times the amount of carbon dioxide in the ocean than there is in the atmosphere.
Carbon dioxide is highly soluble in water. It can move from the atmosphere to the ocean quite quickly, but is slower in moving from the ocean to the atmosphere.
Marine photosynthesis can quickly use carbon dioxide that enters the water.
Carbon dioxide can re-enter ocean and atmosphere cycles via a few processes. Sediments can dissolve back into the water. This can happen because of the pH levels in an area. Geological uplift can expose carbonate rocks to oxygen reactions above water. These reactions can release the carbon dioxide back into the atmosphere. Acid rain achieves the same result when hitting limestone sediments.
Answer to Question 2
False