根据对话内容，补全对话

A: What can I do for you?

B：I want to buy a pair of shoes.

A:____

B: Size eight or nine.

A: Ok! How about this pair?

B: Sorry, I do not like black.____

A: Yes. We have blue, white and brown ones .

B: Can I havea look at the brown ones?

A: Yes, please.

B: ____

A: Forty-sixyuan.        

B: It is too expensive. ____

A: How about forty?    

B: It is still expensive. What about thirty-five?

A: All right.

B: OK.____

从物质的组成角度解释酸具有酸的通性的原因是

小明为探究Cu、Al、Ag的金属活动性顺序，做了如下两个实验．请分析实验，完成填空．

补写出下列句子中的空缺部分。
①苏轼在《赤壁赋》中慨叹人生短暂，并向往大江永恒的名句是“____，____。”

②荀子《劝学》中“____，____”，强调了整天空想不如片刻学***的道理。

③《氓》结尾处回忆了少年时代尽情欢娱的情景，“总角之宴，____”以及恋爱时的盟誓 “____，不思其反。”