完成对话。

Millie: Hi, Sandy,     1  you _____ (start) your history project yet?

Sandy: Yes. I    2   (look) on the Internet to get some ideas, but I     3   (not write)

the report yet.

Millie: What    4   you _____ (decide) to write about?

Sandy: I want to write about Tianjin.     5  you _____ (be) there?

Millie: Yes. I    6     (go) there with my family last year. I think Tianjin    7    

(not change) much.

Sandy: I think there     8   (be) some changes. I    9    already _____ (learn) a lot

about the history of that city.

商品使用价值的研究内容，在量的方面，主要研究（）；在质的方面，主要研究（）。