Answer: a.Amount of pollution decreased.
Explanation: GDP of any country simply gives us the value of final goods produced withing its territory over a given period of time. It does now tell us anything about the standard of living or well-being of its residents. Well-being can decrease when there is high crime rates, over exploitation of workers at work, or when the residents are engaged in illegal activities like drug addiction or smuggling.
However, decrease in the level of pollution will increase the well being of the residents. Therefore, increases in real GDP would understate the well-being of a country over time if the amount of pollution decreased.
