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.

在点燃的条件下，A和B反应生成C和D．反应前后分子种类的变化如图所示：

（1）A、B、C中属于单质的是____ 　（填字母）．

（2）一个B物质的分子是由____ 个原子构成的，B物质中氮元素的化合价是____  ．

（3）若D为空气中体积分数最大的气体，则该反应的基本反应类型是____ ．