The favorite food in the United States is the hamburger. The favorite place to buy a hamburger is a fast food restaurant. At fast food restaurant, people order their food，wait a few minutes ，and carry it to their tables themselves .People also take their food out of the restaurant and eat it in their cars or in their homes. At some fast food restaurant, people can order their food, pay for it and pick it up without leaving their cars. There are many kinds of fast food restaurant in the United States. The greatest in number sell hamburgers, French fries and so on. They are popular among Americans. Besides, there are many fast food restaurants that serve Chinese food, Mexican food, Italian food, chicken, seafood and ice-cream. The idea of a fast food restaurant is so popular that nearly every kind of food can be found in one.

    Fast food restaurant are popular because they reflect (反映) American life style. Customer (顾客) can wear any type of dress when they go to a fast food place .Second, they are fast. People who are busy do not want to spend time preparing their own food or waiting while someone prepares it. In fast food restaurants, food is not expensive. Therefore (因此)，people often buy and eat at a fast restaurant，while they may not be able to go to a more expensive restaurant very often.

已知数列{a_n}中a₁=16,a_n+1-a_n=-2$\left(n\in N^{*}\right)$，则数列{a_n}的前n项和S_n最大时，n的值为 (    ) 

作文：

        题目： 哦，原来这才是____________（哦：表示惊喜、惊奇、领会、醒悟、感叹等）
        要求：先将题目补充完整，写在答题卷上，然后写一篇不少于600字的文章。文内不得出现所在学校的校名、人名、地名，否则扣分。