2、us没有什么严重的事情 be serious about sth.= take sth seriously 严肃对待 a serious illness 一个严重的病5.reduceairpollutionbyridingbicycles.通过骑自行车减少空气污染。reduceairpollution减少空气污染“bydoingsth.”意思是“通过做某事”。6.savewaterbytakingshortershowers通过少洗澡来节约水take/haveashower洗淋浴7.saveenergybyturningoffthelights关灯节约能源t