题目

完形填空Residents of urban areasoften make use of public transportation on their way to school or the office.But when their final 1 isn't near a bus stop orsubway station, those folks have a problem. Transportation experts often 2 to this as the last mile problem —finding a way to close the gap between public transportation stops and one'sdestination.With the last mile problemin mind, the makers of the URB-E 3 a compact electric vehiclethat weighs around 13 kilograms. Unlike bikes, which often don't fit on crowdedbuses or trains, the URB-E collapses into a form 4 to carry-on luggage. And在用滚摆探究“机械能的相互转化”的活动时，把滚摆悬挂在框架上，用手捻动滚摆使悬线缠在轴上，滚摆升到最高点后，放开手，可以看到滚摆下降，越转越______，到最低点时滚摆转而______，直到差不多回到______的位置．滚摆在______位置时重力势能最大，在______位置时动能最大．可见，______和______可以相互转化．