The first material and the second material are about abdication system, and the third material is about hereditary system of the throne. From abdication to hereditary system, China began to move from primitive society to slavery society.

The material 1 means that Yao gave him a good gingerbread suit, a piano, a warehouse and cattle and sheep. This reflects the ancient abdication system. Shun is a foreign surname. You can understand how much a young man can give Yao. I am very grateful to you.