“书山有路勤为径，学海无涯苦作舟”体现了中华民族的传统美德。下列选项同样能够反映这一美德的是（  ）

小明对新型LED灯带很好奇，取一段剖开后发现，灯带中的LED灯是串联后通过电源适配器接入照明电路的，（如图所示）他取下其中一只LED灯接在电池两端没有亮，对调电池正负极后亮了，用手试摸，点亮的灯几乎不发热．以下推断符合上述实验事实的是（）

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      ①这是8年前的旧事。那年，刚过完40岁的生日，突然生出一种莫名的思乡之情。这种感情很强烈，近乎一种烧燎，若不回故乡住上一段日子，心里难以平静下来。于是我回了一趟老家。
      ②到了母亲的老宅院，推开那一道柴门，母亲“哦”了一声，显出意外的喜悦，眼睛潮潮的红起来。走近母亲身边，觉得母亲很矮小，依旧是粗布衣裤，与那道柴门一个色调。多少年了，故乡仍带着那种逼人的质朴。我心里很温暖，觉得自己就是为这质朴而来。
      ③母亲烧起柴草，煮了几穗青玉米。柴草很干，火烧得热烈。“住几天吗？”母亲问。我说：“当然要住几天，陪您唠一唠近20年来不曾细唠的家常。”母亲笑一笑：“你已是老家雀了，只有老家雀才知道回窝哩。”在母亲的感觉里，我居然跟她一样老了。青玉米煮熟了，剥了玉米的苞衣，米粒很黄。一粒一粒剥着吃，很绵软，香得和奶一样。母亲同我一起剥玉米吃。炉膛的余火闪着黄黄的光。我一下子找到了故乡的感觉，即黄色的温暖。
      ④晚上，母亲问我：“你到哪儿睡呢？娘就这一条土炕。”我说：“除了娘的土炕，我哪儿都不去。”躺在土炕上，感到这土炕就是久违了的母亲的胸怀。母亲就是在这土炕上生的我，揭开席子，肯定还能闻到老炕土上胎衣的味道。而今，母亲的儿子大了，自己也老了，却依然睡着这条土炕。土炕是故乡永恒的岁月、不变的情结吗？这一夜，母亲睡不着，她的儿子也睡不着。母亲很想对儿子说些什么，儿子也想对母亲说些什么，却都不知道从何说起，只能清晰地听到对方的呼吸。其实，岁月已使母子很隔膜了，却仍爱着，像呼吸，虽然有时感觉不到，却须臾不曾停止。
      ⑤天亮了，我却酣然地睡沉了。睡醒来，小饭桌早已放在身边。“酒给你温好了，喝几盅吧。”母亲安然说道。饭桌中央，果然就是那把几代人用过的黄泥酒壶。说温酒，其实是把罐中的老酒舀到壶里去。母亲给祖父舀酒，给父亲舀酒，如今，又给她的儿子舀酒，那么，在她眼里，儿子是条有分量的汉子了。
      ⑥在老家的日子，我彻底让自己放松了。每日起得很迟，睡到日上三竿。母亲从不叫醒我，开心地放任她的儿子。“快把娘的儿子宠坏了。”我跟母亲开玩笑。“还能宠几天呢？世道上，除了娘宠儿子，还有谁宠呢？”听了娘的话，我心中竟生出一丝莫名的酸楚。媳妇好，爱情的后面是温柔的束缚；儿子好，伦常会把一副叫责任的担子不由分说地让你担下去；朋友好，友谊时时提醒你要保持一种无奈的却是必须的心灵对等……这一切，都美丽而忧伤，美得让人感到有些累。
      ⑦吃过母亲的早酒，便是走走儿时的路，爬爬儿时的山……路依旧，山依旧，我的感觉却大不一样了。儿时高高的曾绊得我摔破了膝的石阶，已显得很矮很矮。儿时深深地看一眼都眩晕的水井，也显得很浅很浅。山路曲折悠长，我却走来走去，又走回原处。踅回母亲的柴门，看到柴门下的母亲，霜雪已浸染了大片发际。我不禁低沉地吟了一声：“哎，故乡。”
      ⑧晚上，盘腿坐在母亲的土炕上，在小饭桌上摊了几页纸，想随便写些什么。笔落下去，却写出了这么几行字：故乡，就像母亲的手掌，虽温暖，却很小很窄。它遮不了风雨，挡不住光阴，给你的只是一些缠绵的回忆……
      ⑨写到这里，我抬头看一眼熟睡的母亲，想到明天就要走了，泪水不禁热热地流下来。

    Everybody hates it, but everybody does it. A recent report said that 40%of Americans hate tipping. In America alone, tipping is a $ 16 billion-a-year industry. Consumers acting politely ought not to pay more than they have to for a given service. Tips should not exist. So why do they? The common opinion in the past was that tips both rewarded the efforts of good service and reduced uncomfortable feelings of inequality. And also, tipping makes for closer relations. It went without saying that the better the service, the bigger the tip.

    But according to a new research from Cornell University, tips no longer serve any useful function. The paper analyzes numbers they got from 2,547 groups dining at 20 different restaurants. The connection between larger tips and better service was very weak. Only a tiny part of the size of the tip had anything to do with the quality of service.

    Tipping is better explained, by culture than by the money people spend. In America, the custom came into being a long time ago. It is regarded as part of the accepted cost of a service. In New York restaurants, failing to tip at least 15% could well mean dissatisfaction from the customers. Hairdressers can expect to get l5%-20%, and the man who delivers your fast food $ 2. In Europe, tipping is less common. In many restaurants the amount of tip is decided by a standard service charge. In many Asian countries, tipping has never really caught on at all. Only a few have really taken to tipping. According to Michael Lynn, the Cornell papers' author, countries in which people are more social or outgoing tend to tip more. Tipping may reduce anxiety about being served by strangers. And Mr. Lynn says, “In America, where people are expressive and eager to mix up with others, tipping is about social approval. If you tip badly, people think less of you. Tipping well is a chance to show off.”