Task: Question Generation
Input (English): Background Paragraph: Unfortunately, the layer of good ozone is being destroyed by air pollution. The chief culprits are chlorine and bromine gases. They are released in aerosol sprays, coolants, and other products. Loss of ozone has created an ozone hole over Antarctica. Ozone depletion results in higher levels of UV radiation reaching Earth. In humans, this increases skin cancers and eye cataracts. It also disturbs the nitrogen cycle, kills plankton, and disrupts ocean food webs. The total loss of the ozone layer would be devastating to most life. Its rate of loss has slowed with restrictions on pollutants, but it is still at risk. 
Story: Two neighboring habitable planets from the same solar system, planet U and planet N, had Earth-like atmospheres. The inhabitants of planet U destroyed the ozone layer by their actions, while their neighboring planet N didn't.
Output (English): Which planet released less chlorine gas in their atmosphere?