Oceanographer: To substantially reduce the amount of carbon dioxide in Earth' s atmosphere, carbon dioxide should be captured and pumped deep into the oceans, where it would dissolve. The cool, dense water in ocean depths takes centuries to mix with the warmer water near the surface, so any carbon dioxide pumped deep into oceans would be trapped there for centuries. Which one of the following is an assumption that the oceanographer's argument requires? ['Carbon dioxide will dissolve much more thoroughly if it is pumped into cold water than it will if it is pumped into warmer water.', "Carbon dioxide dissolved in cool, dense water in ocean depths will not escape back into Earth's atmosphere a long time before the water in which that carbon dioxide is dissolved mixes with warmer water near the surface.", 'Carbon dioxide should be pumped into ocean depths to reduce the amount of carbon dioxide in the atmosphere only if the carbon dioxide pumped into ocean depths would be trapped there for hundreds of years.', 'It is the density of the water in the ocean depths that plays the main role in the trapping of the carbon dioxide.']