Our school is a green school．What makes it green？

    First，we have a lot of trees．There are trees in front of and behind every building．Some trees are green only in spring and summer．And some are green all year round．The trees make our school look like a big forest.

    And our school is a green one because we "go green". How do we go green？We have two green days every month．On green days，no students or teachers go to school by car．And we have clean﹣up Day every month．That day，students go to streets to pick up rubbish．Also，we have tree﹣planting Day every spring．We plant young trees on hills．We have three green clubs The members of the clubs look after those trees well．

    Green is not only a colour．It is about life．Please go green with us and make the world a more beautiful place．

    每当夜间疲倦，正想偷懒时，仰面在灯光中瞥见他黑瘦的面貌，似乎正要说出抑扬顿挫的话来，便使我忽又良心发现，而且增加勇气了，于是点上一枝烟，再继续写些“正人君子”之流所深恶痛疾的文字。

已知△ABC三边长都是整数且互不相等，它的周长为12，当BC为最大边时，求∠A的度数．

世界各大洲中，人口最多的是（   ）