新鲜空气(Frsh Air)popl in villags ar halthir than popl in towns. that is bcaus th air in villags is vry frsh. farmrs ar working all day in th filds, brathing frsh clan air. but thr ar too many factoris in citis.thy produc mor and mor harmful gass. at last, citis ar full of smok. and thr's many dust in citis,too. it may caus a disas. so frsh air is vry important to th popl in citis. w nd frsh air. so plas don't pollut th air!