54. Something must be done to improve the conditions of buses for their public use.
Something has been done to stop polluting the rivers and lakes.
Some measures must be taken to ban the teenagers from playing video games after school without doing their homework.
一些事情必须要做，来提高公共汽车的使用情况。一些事情应该去做，阻止污染河流与湖泊，一些措施必须采取，来禁止一些少年放学后不做作业来玩电子游戏。
55. We should do our best to act politely in public places. / mind our manners in public.
我们应该尽自己最大的努力在公共的场所做的有礼貌。
