Central idea:
The poet praised the magnificent Yellow River with a long history and inspired Chinese sons and daughters to follow the example of the Yellow River and learn its "greatness and strength".
The general idea of this paragraph is:
On the first floor (from "I" to "North and South"), the image of the Yellow River seen by writing "I" highlights the irresistible momentum of the Yellow River.
On the second floor (by "ah! Yellow River! " To "develop and grow"), eulogize the great Yellow River spirit from three angles.
The third layer (the last four lines) expresses the determination of the sons and daughters of the motherland.