Task: Question Answering
Input (English): Background Paragraph: Recall that air pollution is due to chemical substances and particles released into the air mainly by human actions. When most people think of air pollution, they think of the pollution outdoors. But it is just as easy to have indoor air pollution. Your home or school classroom probably doesn't get much fresh air. Sealing up your home reduces heating and cooling costs. But this also causes air pollution to stay trapped indoors. And people today usually spend a majority of their time indoors. So exposure to indoor air pollution can become a significant health risk. 
Story: Two neighboring cities had very different health related problems. Twin city had increased air pollution, their people experiencing all kinds of respiratory diseases, while Pine city had problems with age related diseases. 
Question: Which city had more people exposed to chemical particles released into the air by human actions?
Output (English): Twin.