关于声现象，下列说法中正确的是（　　）

水、土是立国之本，我国水和耕地资源的分布情况是（　　）

在完全显性条件下，下列各杂交组合的所有后代中，与双亲具有相同表现型的是（　　）

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.

 在化学反应中，凡是元素化合价发生改变的反应，称为氧化还原反应．配平这类反应方程式往往采用“化合价升降法”更方便快捷，即反应中元素“化合价升高总数=化合价降低总数”．

例如：□Al+□MnO₂═□Al₂O₃+□Mn，具体配平步骤如下：

①“标变价”：找出化合价发生改变的元素，并标出改变前后的化合价．

4$\stackrel{0}{Al}$+3$\stackrel{+4}{Mn}{O}_2$═2$\stackrel{+3}{A{l}_2}{O}_3$+3$\stackrel{0}{Mn}$

②“列变化”：列出改变的价态数．

$\stackrel{0}{Al}$$\to$$\stackrel{+3}{Al}$ 升高3价 $\stackrel{+4}{Mn}$$\to$$\stackrel{0}{Mn}$降低4价

③“找倍数”：找出化合价升、降的最小公倍数为3×4=12，从而确定Al、MnO₂的系数．

4Al+3MnO₂═2Al₂O₃+3Mn

④“配系数”：再用观察法，配平其它系数．

4Al+3MnO₂═2Al₂O₃+3Mn

根据以上信息，结合已学知识，回答下列问题：