“大河有水小河满，小河无水大河干。”这启示我们 （）
①个人利益比集体利益更为重要
②集体利益是所有个人利益的总和
③集体利益的实现离不开个人的努力
④只有维护集体利益，个人利于才有保障 

顾炎武在《日知录》一书中说："易姓改号，谓之亡国。仁义充塞， ……，人将相食，谓之亡天下"。"亡国"和"亡天下"两个概念，其中"亡天下"的确切含义是

读一读，补全对话。

A. What about you?            
B. How old is your cousin?

C. Do you have any cousins?    
D. What is his name?
 Ann: Hi! Mike.____
Mike: Yes, I have one cousin.
Ann: ____
Mike: He's 9 years old. ____
Ann: I have one cousin, too. He's a boy.
Mike: ____
Ann: His name is Dan.He is 10 years old.

CaCO₃+2HCl ====    ____        +     ____       +    ____