C) Northern to Southern
Option c. The population shift from northern to southern China occurred during the years of the Song dynasty.
The Song dynasty was an imperial dynasty of China that began in the year 960 and lasted until the year 1279. The dynasty's history is divided in two different periods: Northern Song and Southern Song. From 960 until 1127 the dynasty's capital was located in the Northern city of Bianjing and the North dominated the whole area. But in 1127 the Northern Song lost its control of the area to another dynasty called Jurchen-led Jin causing the population shift of the Song dynasty from the North to the South, where they all retreated to. From there one until 1279 the Song dynasty was located in the south of China.