Question 7: The reservoir that stores the most carbon as measured by gigatons (Gt) is Rocks. While fossil fuels and oceans also store significant amounts of carbon, geological formations (rocks) contain the largest amount of carbon in the Earth's system.
Question 8: The reason Earth's atmosphere contains a relatively small amount of carbon dioxide compared to other carbon reservoirs like the ocean and rocks is: Most atmospheric CO2 dissolves into the ocean due to ocean circulation patterns. The oceans act as a major sink for carbon dioxide, absorbing it from the atmosphere.