Question

Which would most likely be the subject matter of a song dynasty painting?

Answer 1

The Song Dynasty is period of Chinese history. The period began in 960 and continued until 1279 and was a period with very rich culture. The most popular art work from this period is ink painting, specifically of natural scenes and landscapes.
The subject matter of a Song Dynasty painting most likely would be a detailed landscape of a mountain valley. 

Answer 2

During the Song dynasty most likely landscapes would be painted to  show things with relative permanency compared to the changes in society and also to show the natural hierarchy as a metaphor for a successfully regulated state.