如图所示为一个生态系统中某些生物的相对数量关系，这些生物构成了一条食物链．在这条食物链中物质和能量流动的方向是（  ）

闭着眼睛的男孩

毛小懋

       ①走进青眉山小学的第二天，我给孩子们布置了一篇作文。题目很简单：我喜欢……

       ②第三天早晨，我就知道了有的孩子喜欢篱笆上的牵牛花和枣树林里的知了，有的孩子喜欢在秋天的岭上追野兔子，有的孩子喜欢把毛毛虫放进女同学的文具盒里，有的孩子喜欢沉默，曾经一连九天一句话也不说。

       ③还有一个孩子，叫聂国柱，他的作文让我吃了一惊：A我喜欢闭着眼睛，尤其是爸爸打我的时候。奶奶说，闭着眼睛，巴掌打在身上就不疼了，心里就不难过了。打完了，睁开眼睛，就能把刚才的事忘了，就像没有挨过打一样。

       ④下课后，我把聂国柱叫进了办公室。他是坐在教室角落里的一个男孩，四肢很细，脑袋很大，像谷穗一样沉甸甸地低垂着。我翻开他的作文簿，问：“你爸爸经常打你，是真的吗？”聂国柱重重地点了点头。“他为什么打你？”聂国柱咬着嘴唇，迟疑地说：“他是一个酒鬼，每天都喝酒，喝了酒就要打人。”

       ⑤我是新来的老师，颇急于在孩子们心中树立威信。我觉得现在是一个机会，于是站起来说：“走，带我去你家，我跟你爸爸谈谈。”说着我牵起了聂国柱的手。不料，聂国柱轻轻地挣脱了我的掌握，低着头说：“不管用的，我爸爸不会听你的，”顿了顿，他补充了一句:“去年陈老师也跟我爸爸谈过，一点用都没有。”我尴尬地愣住了。陈老师是我的前任，她是一个能说会道的人，她甚至说服了不善言谈的我，来青眉山小学为她代一年的课。

       ⑥聂国柱接着说：“我爸爸喝醉酒就管不住自己了，一定要打人，家里只有奶奶和我，他不能打奶奶，只能打我了。”我不知道说什么，只能安慰他：“过几天，我一定给你想一个办法。”聂国柱点点头，慢慢地退出了办公室。

       ⑦我给在县医院养病的陈老师打了一个电话。陈老师说，跟聂国柱的爸爸是不能讲道理的，越蛮横才越有效果。于是，我想出一个办法，晚上把聂国柱留在了我的宿舍里。当天晚上，聂爸爸很着急，问遍了全村。他当然问不出结果，因为班上所有的孩子都在帮聂国柱。第二天，聂国柱继续上课，晚上继续住在我的宿舍里。

       ⑧聂爸爸心急如焚，酒都顾不上喝了。第三天晚上，他在村口的打麦场里放声大哭，边哭边打自己的耳光，说一定是自己的巴掌打走了儿子。班上的孩子发现了，飞跑来告诉了我。我急忙带着聂国柱去打麦场。聂国柱也哭出声来，扑在了爸爸的怀里。

       ⑨事情就是这么简单而神奇，从此聂爸爸再也不打聂国柱了。

       ⑩年底的最后一堂作文课，我让孩子们练习写人物。聂国柱写的是《我的奶奶》：“我的奶奶头发很白，眼睛很大，但是她总是闭着眼睛，你知道是为什么吗？因为她是一个盲人。奶奶曾经告诉我，受欺负的时候，只要闭上眼睛，心里就不会难过了。我试过很多次，其实一点也不灵，但是受欺负的时候，我还是会闭上眼睛。因为，奶奶是世界上最疼我的人，闭上眼睛我就能看见奶奶看见的世界，我就知道我和奶奶在一起了……”

       ⑪我站在讲台上。把聂国柱的作文读给孩子们听。孩子们都羡慕地扭头去看聂国柱。B聂国柱躲在角落里，激动得手指都在颤抖，两只大眼睛羞怯地盯着课本。

       ⑫读完一半，我抬头朝聂国柱微笑，却看见他慢慢地闭上了眼睛，眼角似乎掉下了一颗闪亮的泪滴。

（选自《新小读者》，有删减）

方程$x^2+y^2+4mx-2y+5m=0$表示圆的充要条件是

    Age has its privileges in America, and one of the most important of them is the senior citizen discount. Eligibility(资格) is determined not by one's need but by the date on one's birth certificate. The discounts have become a routine part of many businesses—as common as color televisions in motel rooms and free coffee on airliners.

    People with gray hair often are given the discounts without even asking for them; yet, millions of Americans above age 60 are healthy and solvent (有支付能力的). Businesses that would never dare offer discounts to college students or anyone under 30 freely offer them to older Americans. The practice is acceptable because of the widespread belief that ＂elderly＂ means ＂needy＂. Perhaps that once was true, but today elderly Americans as a group have a lower poverty rate than the rest of the population. To be sure, there is economic diversity within the elderly, and many older Americans are poor. But most of them aren't.

    It is impossible to determine the impact of the discounts on individual companies. For many firms, they are a stimulus to revenue. But in other cases, the discounts are given at the expense, directly or indirectly, of younger Americans. Moreover, they are a direct irritant(刺激物) in what some politicians and scholars see as a coming conflict between the generations.

    Generational tensions are being fueled by continuing debate over Social Security benefits, which mostly involve a transfer of resources from the young to the old. Employment is another sore point. Supported by laws and court decisions, more and more older Americans are declining the retirement dinner in favor of staying on the job—thereby lessening employment and promotion opportunities for younger workers.

    Far from a kind of charity they once were, senior citizen discounts have become a privilege to a group with millions of members who don't need them.

It no longer makes sense to treat the elderly as a single group whose economic needs deserve priority over those of others. Senior citizen discounts only enhance the myth that older people can't take care of themselves and need special treatment; and they threaten the creation of a new myth, that the elderly are ungrateful and taking for themselves at the expense of children and other age groups. Senior citizen discounts are the essence of the very thing older Americans are fighting against—discrimination by age.