设整数. 若存在实数$t$，使得$t=1$，$t^2=2$，…，$t^n=n$ 

同时成立，则正整数n的最大值是（    ）

天然气的主要成分是甲烷，液态的氢气可以做火箭推动剂．为了探究甲烷和氢气的燃烧有什么不同，分别在空气中点燃甲烷和氢气，在甲烷火焰上罩一个冷而干燥的烧杯，发现罩在火焰上方的烧杯内有水雾产生，倒转过来，向烧杯中倒入少量澄清石灰水，振荡，石灰水变浑浊，说明甲烷燃烧产生了____又产生了____，其燃烧的文字表达式为____，在氢气火焰上罩一个冷而干燥的烧杯，烧杯内有水雾产生，倒转过来，向烧杯中倒入少量澄清石灰水，振荡，石灰水未变浑浊，说明氢气燃烧产生了____，由此得出结论：甲烷与氢气的成分____（填“相同”或“不相同”）．

危楼____，手可____。

____高声语，恐惊____。

敕勒川，阴山下，

____

天苍苍，野茫茫，

____

    I have eight teachers now and I love them. My favorite teacher is my English teacher, Sophia.

    Sophia is an English woman. She loves Chongqing. She thinks Chongqing is great. She loves Chongqing food.她早餐吃什么？Bread and milk? No. She only has noodles (面条)。 Hot pot(火锅)is her favorite . She always eats it in the evening on Friday .Sophia has a daughter and a son. They are eight.他们去相同的学校。 They like hot pot, too. They are in Chongqing,too.

    My classmates like to play English games with Sophia. When we have questions, we like to ask her for help.

阳光小学六年一班有39人去水上乐园玩，他们看了门口的价格表，正在商议如何购票．请你帮他们设计出几种购票方案，哪种最省钱？

水上乐园售票价格表