公平，是社会主义和谐社会的重要内容。下列举措中不能体现社会公平的有（  ）

①城乡义务教育全部免除学杂费        ②积极开展大课间体育活动

③加快城乡社会保障体系建设            ④开展“禁烟一小时，亿人健康行”活动

请根据图中通电螺旋管的N极，标出磁感线的方向和小磁针的N极，并在括号内标出电源的“+”、“﹣”极

增加：在缺词处加一个漏词符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下面划一横线，并在该词下面写出修改后的词。

注意：1). 每处错误及其修改均仅限一词；、

2). 只允许修改10处.多者（从第11处起）不计分。

    When we play football on our school's football field, we have got be very careful. That's because of there is an ancient tree growing in a middle of it. Our school is surround by many historical building. When we decided to turn the only available space into a football field, we find the tree had to be removed. We asked for permission to have it removed anywhere else, and it was too risky because the tree is considered as a national treasure. Final, we decided to build the field around it. I consider the tree as a great symbol of our school.