禁止近亲结婚的目的是（　　）

在一个大型平底烧瓶湿润的泥沙中插上几枝新鲜的枝条和一支盛有适量NaOH溶液的试管，烧瓶口紧包一个气球，使烧瓶悬浮在玻璃缸中某一位置（如下图）。自然环境下持续观察，最终可以发现烧瓶的浮沉情况怎样？请解释其中的原因。

假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。

增加：在缺词处加一个漏字符号(∧)，并在其下面写出该加的词。

删除：把多余的词用斜线(\)划掉。

修改：在错的词下划一条横线，并在该词下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词。

        2）只允许修改10处，多者(从第11处起)不计分。

    As is known to we all, America's national pastime is baseball. It has played in the country since the first settlers arrive. It was a national ball what was liked by many Americans at that time. Although baseball possibly developed from an English game, it is now thought of like an American sport. From the Little League to the Major League, player of all skill levels enjoy testing their power on the “ Field of Dreams”. Famous players, exciting music but the standard stadium food of hot dogs, popcorns and peanuts are popularly among Americans. In a fact, Americans make go to the baseball game a favorite summer outing for many Americans nowadays.