yysj (第31/57页)

　less　air.　We　live　in　air，　but　we　ot　see　it.　We　　only　feel　it　when　it　is　moving.　Moving　air　is　called　wind.　How　　we　make　air　move?　Here　is　one　way.　Hold　an　open　book　in　front　of　your　face，　close　it　quickly.　What　　you　feel?　What　you　feel　is　air.

    Passage　29.Clocks

    There　are　many　clocks　in　the　Brown’s　house.　They　are　in　different　rooms.A　big　clock　stands　in　a　er　of　the　sitting　room.　It　is　a　very，　very　old　clock，　but　it　still　keeps　good　time.　Mr.　Brown　winds　it　once　a　week.

    Passage　30.　Swimming

    Swimming　is　a　good　srt.　It’s　pur.　People　like　swimming　because　the　water　makes　people　feel　cool.　But　if　they　swim　in　a　wrong　pce，　it　is　very　dangerous.　These　years，　some　p