先阅读短文，掌握其大意。然后从方框中所给的词中选出恰当的10个，并用其适当形式填空，每个词限用一次。(每小题1分)

stop, though, sleep, their, bad, city, ill, we, start, fresh, please, breath

    Villagers are healthier than people who live in towns. One reason for this is that country air is   than the air in smoky    . The villager is     fresh clean air all day in the fields, but the air the townsman breath is always full of smoke and dust. We cannot live without air. If we are     from breathing even for five minutes, we will die. Bad air means bad health and certain kinds of    , which may kill us,     they may not kill us at once.
We all know     feelings we will get if we stay a long time in a shut, crowded room. After a time, we begin to feel very      , and can hardly keep our eyes open. Then our heads begin to ache, and the longer we stay the     we feel. How nice it is when we get outside into the fresh air! We must, therefore, keep     windows open, so that air in our rooms is always fresh.