【正确答案】：
The notion of thematic progression concerns the ways that texts develop the ideas they present. More specifically, it concerns where Themes come from and how they relate to other Themes and Rhemes of the text.
In linear thematic progression, the content of the Theme of a second clause (Theme 2) derives from the content of the previous Rheme (Rheme1), the content of Theme 3 derives from Rheme 2, and so on, as in example below. 