看图填空．

进入青春期以后，同学们对于男女同学之间的关系看的很是微妙，如果有男同学和女同学走的近，就会有人在背后指手画脚，对这种情况，你的认为是（    ）

热带雨林生态系统与草原生态系统比较，前者维持生态平衡的能力更强．

完成对话。

Salesgirl: Can I help you?

Mary: Yes. I want a skirt.____?

Salesgirl: It's eighty yuan.

Mary: It's too expensive. ____?

Salesgirl: Yes, we do. This skirt is only thirty-five yuan. ____?

Mary: Medium.

Salesgirl: And ____?

Mary: Yellow color.

Salesgirl: Do you like this yellow skirt?

Mary: Yes, I like it.

小雨用电热水器将水加热．他洗完头发开窗通风时被风一吹感到凉．他看到妈妈腌的鸡蛋悬浮在盐水中．请用…（开头4个字）…（结尾4个字）将你所选的内容写出来，并用所学的知识进行解释．