四面体ABCD中，AD与BC互相垂直，AD＝2BC＝4，且AB＋BD＝AC＋CD＝2$\sqrt{14}$，则四面体ABCD的体积的最大值是(     )

阅读下面文字，按要求作文。

    岁月匆匆，十二三岁的我们已经走进花样的季节，站在由少年走向青年的门槛上，清点行囊，我们会发现自己多了一份成熟，少了一份幼稚；多了一份拼搏，少了一份幻想；多了一份感恩，少了一份淡漠；多了一份关爱，少了一份自私；多了一份责任、理想与憧憬……我们的行囊变得沉甸甸的，我们的道路正在向来来延伸。

请以“今天，我多了一份_______”为题，请先补充题目，使题目完整，写一篇500字以上的有真情实感的文章。

要求：①请将题目补充完整；②文中不得出现真实的人名、校名、地名；③叙述清楚，中心明确，感情真挚，字迹工整；④500字以上。

易水诀别中，既有对群体人物的描写，也有对主人公的直接描写，其中荆轲用唱词“____，____”直接表达了自己对刺杀秦王一事的悲壮心情。(《荆轲刺秦王》)

Two Trips

Jack brought a small plane and began to fly it． He soon became excited and made his plane all kinds of tricks．

Jack had a friend，named Tom． One day Jack said to him，“I will pick you up in my plane．““I will be glad to．'answered Tom． They went up，and Jack flew around for half an hour and did all kinds of tricks in the air． Then they came down． Tom was to be back safely，and said to Jack，“Well，Jack，thank you very much for those two trips in your plane．“Jack was very surprised and asked，“Two trips？““Yes，my first and my last．'an﹣swered Tom．

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