按照动力维护规程规范，三相供电电压不平衡度不大于（）。电压波形正弦畸变率不大于（）。

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 小题1:  than the air in smoky   小题2: . The villager is   小题3:  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   小题4:  from breathing even for five minutes, we will die. Bad air means bad health and certain kinds of   小题5: , which may kill us,   小题6:  they may not kill us at once.
We all know   小题7:  feelings we will get if we stay a long time in a shut, crowded room. After a time, we begin to feel very    小题8:  , and can hardly keep our eyes open. Then our heads begin to ache, and the longer we stay the   小题9:  we feel. How nice it is when we get outside into the fresh air! We must, therefore, keep   小题10:  windows open, so that air in our rooms is always fresh.