What is the official language of the Southern Song Dynasty?

Analysis:

After the demise of the second year of Jingkang in the Northern Song Dynasty (1 127), a large number of people in the Yellow River basin moved southward, and the immigration tide continued until the end of the Southern Song Dynasty. From the first year of Shaoxing (1 13 1), Lin 'an (now Hangzhou) was the "temporary capital" of the Southern Song Dynasty and the political center of the South from 143. Therefore, most of the royal family, civil and military officials, businessmen, scholars, citizens, soldiers and monks and nuns who moved south from Kaifeng, the capital of the Northern Song Dynasty, concentrated in Lin 'an. Because of their special status, large number and concentrated residence, these immigrants still speak Kaifeng dialect after settling in Hangzhou, so they formed a Kaifeng dialect area in Hangzhou. There are also immigrants from other parts of the north in Hangzhou. Their native dialect is very different from Hangzhou dialect, but it is close to Kaifeng dialect, so they will naturally choose to move closer to Kaifeng dialect. Kaifeng dialect has become the official language of the imperial court and the strong language of Hangzhou. In order to deal with the dominant Kaifeng people, the aborigines in Hangzhou have to be officials, go to school, do business and be servants, so they can only learn Kaifeng dialect. Over time, Kaifeng dialect became Hangzhou dialect, completely replacing the original dialect.