【導(dǎo)讀】Wecannot____it,butwecan____it.Airis__________.Theyallneedittoo.Wecannotseeit,butwecanfeelit.Itiseverywhere.Theyallneedittoo.Whatisit?Itisair.Airkeepsusalive.It’sthesmoke.Hereyeshurt.Whathurtshereyes?What’sthematter,Kitty?Areyoucrying?It’sthesmoke.Let’sgotothepark,Ben.OK.theairclean.Yes!Howistheair?It’sdirty.It’sdirty.It’sclean.