近来，我国一批腐败高官纷纷落马，受到了法律的制裁。这说明（   ）

已知数列$\left\{a_n\right\}$满足_{$a_{n+1}=\left\{\begin{array}{c}2a_n\left(0\le a_n<\frac{1}{2}\right)\\ 2a_n-1\left(\frac{1}{2}\le a_n<1\right)\end{array}\right.$，}若$a_1=\frac{6}{7}$，则$a_{2008}$的值为(      )

用化学用语填空：空气中含量最多的气体____ ；氧化铝中铝元素显+3价　____ ；硝酸铵中的阳离子____ ；人体内含量最高的金属元素　____ ．

507×46=____762÷19=____36×126=____226÷54=____

阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中单词的正确形式填空
    Do you know how to be a top student? Top students are decided by a new way now. New rules for middle school students ____ (come) out in March. The best students should not only have good grades. You'll be a top student ____  you follow the new rules.____  (one), you need to be honest. You should never copy others’ homework. Second, good students love animals and care____ other people. They try to do something to protect animals, too. Are you one of them? Third, you should learn that teamwork____  important. So be friendly to the people you are with and it can make your team stronger.