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: Planet Y and planet X were two inhabited planets in a nearby solar system. People from Planet X were living in harmony with nature, and didn't hurt the environment in any way. People on planet Y generated lots of air pollution, and destroyed their ozone layer by using inappropriate substances.
Output (English): Which planet has fewer chlorine gases in their atmosphere?