阅读下面短文，从短文后各题所给的四个选项(A、B、C和D)中，选出一个最佳选项。   
    “Daddy, can I have a piece of cake？” my oldest son asked me.
We had just been to the gym and stopped to eat at the restaurant.
    “No，” I replied, “you don't need a piece of cake.”
My son 1 15 in a few days. He 2  over 6 feet tall. He is very slim and athletic in shape . It was not always that way. My wife wrote a book about the challenge and   3   of getting him fit. He now takes it  4  and looks as if he's never been overweight in his life.
    He had a full plate of vegetables and tofu.  He didn't need a piece of cake.  5 ， everything in the restaurant is quite  6 . Our dinners could have  7 a family of seven at a fast food restaurant. That cake probably  8 $5.
    He was silent as he looked at the delicious cakes. I had forgotten that I had walked over to the cake shelf while he was   9 his food from the buffet (自助餐)．
    I looked at my plate. There sitting on the edge was a piece of 10. I looked at it wondering but also knowing how it got there. “We will divide it，” I said.
    A few days later my oldest son was  11me again. We stopped at a   12  . He ordered a sandwich. I then13 two sandwiches. He immediately barked, “Can I have two？” He wanted 14what Daddy had.
    Your kids are very   15 to put on their trays, exactly what you have on yours, and I think this applies to (适用于) more than food. Keep your life plate with only what you want your kids to have.

Teenagers should be allowed to choose their own clothes.青少年应该被允许选择他们自己的衣服。

①allow sb to do sth. 允许某人做某事(主动语态)如：

Mother ____ every night. 妈妈允许我每晚看电视。

②be allowed to do sth. 被允许做某事(被动语态)如：

Lily ____. 莉莉被允许去广州。

阅读以下材料，回答相关问题．

据多家北京媒体报道，北京市首条中低速磁悬浮交通线路S1线如今已基本全线开工建设，预计将于2016年底开通运行．资料显示，这条磁悬浮线路将连接北京西部的门头沟新城和石景山区苹果园站，线路全长10236米，其中高架段9953米，隧道段283米，共设车站8座，全部为高架站．线路运营初期将配备10列中低速磁悬浮列车，该列车由6节车厢编组而成，长约94米、宽3米，整列车最高可容纳1032个乘客，整车采用高铁车辆广泛应用的铝合车整体结构，外观简洁且富有现代感，在防火安全、隔音降噪、乘坐舒适性方面达到国际标准．

北京市磁悬浮S1线采用的是自主知识产权的中低速磁悬浮技术，列车时速只有100﹣120公里（1公里等于1千米），对环境影响大大降低．相比传统轨道交通，中低速磁悬浮具有节能、环保、噪音小、转弯半径小，爬坡能力高等特性，造价略高于轻轨，而远低于地铁．

磁悬浮线路产生的辐射会不会过大？专家介绍说，中低速磁悬浮列车行驶时，1米距离的辐射值比日常使用的电磁炉表面还要低，3米外的辐射值比微波炉辐射值的一半还低，到了5米远，辐射值比使用电动剃须刀还要小，而到了10米距离，其辐射量完全淹没在环境背景中，专业的检测仪器都检测不到了．

线路周边居民也不必对列车噪音问题过分担心．“运行期间，列车将浮起约1厘米．”列车生产企业中国北车技术人员向记者介绍，S1线中低速磁浮列车的运行，依靠电磁铁与轨道产生的电磁吸力使列车浮起，车身与轨道之间保持一定的气隙而不直接接触，从而没有了轮轨激烈摩擦的噪声．

按能量由低到高的顺序排列，正确的一组是（   ）

2014年4月22日是第45个世界地球日，活动主题确定为“珍惜地球资源转变发展方式——节约集约利用国土资源共同保护自然生态空间。”据此回答问题。